The Masterbuilder_March 2012_Formwork and Tunneling Special

MB Cover

Hyderabad Industries Ltd

Hess Concrete Machinery India (P) Ltd

Metecno India Pvt.Ltd

Hyundai Construction Equipment India Pvt.Ltd

Greaves Cotton Ltd

Fayat Group

EDITOR'S COMMENT Your feedbacks are welcome and should be sent to: The Editor, The Masterbuilder, 102/11 (New No. 46/11), Tripti Apartments, Marshalls Road, Egmore, Chennai, India. Phone: +91 44 28555248 Telefax: +91 44 28586703

Encouraging Signals

A

n economy is the method through which a nation prepares today so as to afford the improvements of tomorrow a thought widely believed and conceived. Aligned with this thought is the current scenario where the infrastructure sector is one of the thrust areas in the recent budget, as finance minister Mr. Pranab Mukerjee announced a slew of proposals, including allowing financial institutions and others to raise about ` 60,000 Crores from tax-free bonds and envisaging a greater private participation. Most industry captains I had a dialogue with, post-budget, believe the government has given a much-required push to the infrastructure sector through flagship programmes and nodal organisations such as NHAI that is responsible for spear-heading the progress of change in the sector. By allowing these organisations to raise ` 60,000 Crores through tax-free bonds, UPA II, he has clearly demonstrated the government's intention to provide the much needed financial support to these organisations. Increase in investment in the sector has been envisaged through a combination of public investment and public private partnerships (PPP).To attract private investment in specific sectors such as irrigation, oil and gas storage facilities and telecommunication provisions has been made to provide stakeholders with viability gap funding (VGF) under the scheme 'Support to PPP in Infrastructure'. The finance minister in his budget speech reiterated the need for significant investment in various infrastructure sectors. Government's dependence on private sector for augmenting the investment through PPP route was also emphasised. Mr.Pranab Mukerjee has also provided more avenues of raising funds with measures like relaxing external commercial borrowing (ECB) guidelines, reductions in withholding tax (WHT) and proposal to remove cascading effect of dividend distribution tax (DDT). Also, the government has approved the guidelines for establishing joint venture companies by public sector undertakings in defence sector through the PPP mode. To encourage PPP in road construction projects, the finance minister has permitted ECB for capital expenditure on the maintenance and operations of toll systems for highways. The allocation to the highways sector has also been enhanced by 14 per cent to ` 25,360 Crores in 2012-13 with a target of covering a length of 8,800 km roads under NHDP next fiscal. On the whole the current budget should pave way for the country to grow progressively at a rate of close to 7% in spite of the formidable challenges it may face in the coming days. A number of recent economic reports have vividly predicted that by 2015 India will begin to outpace China in terms of annual GDP growth rate. However, the immediate objective should be to take the country into a double-digit growth trajectory. This target is quite realisable, provided India unleashes its full potential and dares to challenge the hurdles that have been restricting its growth engine from going full throttle. And now there are also some encouraging signals to this effect. Foreign direct investment (FDI) into India has gone up by an impressive 56 per cent to $2.53 billion recently, indicating improvement in investor sentiment. The current edition of the magazine attempts to disseminate valuable information on modern day methods, materials and practices in the field of corrosion, formwork and tunnelling for the benefit of our readers. We hope you enjoy the current edition and as always, we are all ears to know what you think. Regards

K.P Pradeep, Editor-in-Chief [email protected]

FORM IV: The Masterbuilder Place of publication: Chennai, Periodicity of Publication: Monthly, Printers Name: Ashok Natarajan, Nationality: Indian, Address : Times Printers & Publishers, No.57 (29), Dr. Besant Road, Ice House, Chennai - 600 014 Publisher's Name: K P Pradeep, Nationality : Indian, Address : MB Publishers Pvt. Ltd, No.102/11, Tripti Apartments, Marshalls Road, Egmore, Chennai - 600 008. Editor's Name: K P Pradeep, Nationality: Indian, Address: MB Publishers Pvt. Ltd, No.102/11, Tripti Apartments, Marshalls Road, Egmore, Chennai - 600 008. Names and addresses of individuals who own the newspaper and partners or shareholders holding more than one percent of the total capital: K P Pradeep, No.102/11, Tripti Apartments, Marshalls Road, Egmore, Chennai - 600 008. Nigel Narayan, No.102/11, Tripti Apartments, Marshalls Road, Egmore, Chennai - 600 008. Declaration I, K P Pradeep, hereby declare that the particulars given above are true to the best of my knowledge and belief. Date: 25/March/2012 Sd/-

K P Pradeep

Editor-in-Chief K.P. Pradeep [email protected] Vice-Chairman K G K Moorthy [email protected] Director Editorial, Construction Chemicals Dr. Y P Kapoor Editor-in-Charge Ravi Damodaran Sub-Editor Nigel Narayan Head - Content Development CE, Infrastructure & Environment Sadagopan Seshadri Contributors Bhavani Balakrishna, Saadat Ali, Sanjay Staff Correspondent M.K. Prabhakar Vice President Marketing H. Usha Devi Head-New Media Initiative Pradeep Nair Credit Controller G.B. Muralidharan Finance R. Prema Manager Digital Production K. Sravanthi Kiran Manager Digital Media Lakshmi Creative Head S. Nithiyanandam Production Manager Caroline D'sylva Digital Production Assistant R. Anand Subscription & Circulation Team R. Mariya Selvi, Sateesh Kuniyil, S. Sasi Corporate Office MB Publishers Pvt. Limited 102/11 (New No. 46/11), Tripti Apartments, Marshalls Road, Egmore, Chennai - 600 008. Ph: 044-28555248 Telefax: 28586703. Subscription & Circulation [email protected] Website www.masterbuilder.co.in Karnataka No.40, 2nd Floor, 7th "C" Cross, Ashwini Layout, Koramangala, Bangalore - 560047. Phone: 080 - 25701079 / 25705888 Mobile: 09343833191 Owned and Published by K.P. Pradeep 102/11 (New No. 46/11), Tripti Apartments, Marshalls Road, Egmore, Chennai - 600 008. Printed By Ashok Natarajan Times Printers & Publishers, New No. 57 (29), Dr. Besant Road, Ice House, Chennai - 600 014. Disclaimer All rights reserved. Reproduction in whole or part without prior written permission prohibited. The views expressed in this magazine are those of the authors and do not necessarily reflect those of the management.

Gandhi Automations Pvt.Ltd

Eventful March The month of March, financially the most critical month in the Indian economy, the month that sets in the mercury heat across the country, and the Union Budget presentation, surely qualifies to be the most eventful period in the year. While the drama surrounding the announcement of the Railway Budget completely overshadowed the announcements in the budget itself, the Union Budget 2012-13 did not have major surprises waiting for the industry, as was expected by industry captains. The UPA, in the aftermath of electoral setbacks in UP seems to have played it safe this time around. While there are some positive measures announced for the infrastructure sector, it remains to be seen as to how the government is able to push further policy reforms such as FDI in retail and aviation in the near future. Along our journey to become the premier construction magazine in the country, we have always settled for nothing but the best. We are also forever fuelled by the results of our hard work - delivering the highest quality of content to our readers. As we march towards our goals, this month surprised us with a booster, and awards immemorable. We received the Vishwakarma Award from The Construction Industry Development Council (CIDC) for the Best Online Construction Magazine and Best Journalist 2012. We followed this up with another award from the Builder Association of India (BAI-Southern Region) for Best Construction Magazine. These awards not only recognize our high value for content but also our innovative routes to market in the dynamic era that we belong to. It's great to be recognized for our achievements, but our focus is still remains steady on the road ahead, driven to be and remain the most comprehensive civil engineering magazine in the country. I also take this opportunity to thank all our readers, advertisers and well wishers for accepting our invite to attend the recently concluded International Construction Chemicals Conference (C3) organized by CCMA. The conduct of C3 could not have been timed better as we enter a crucial second phase of infrastructure development and the eyes of almost every other industry is towards the construction sector. The larger scale of projects, which has pushed up demand for high-strength and quick setting concrete, plus the greater emphasis on quality, has automatically made a positive impact on the construction chemicals market. The growth story of CCMA also makes for fascinating reading. It is really interesting since it is perhaps the only industry association whose members are engaged in intense competition in the marketplace, a point that was bought out Mr. R. K. Jha, Director, Gujarat International Finance Tec-City (GIFT), during his inaugural address at the conference. The association has grown to include over 35 member-manufacturers within a remarkably short span of time. C3 saw every top player in the field of construction chemicals rub shoulders with each other, all for the greater cause of the promotion of the industry, something that is remarkable in this day and age of intense competition.

K.G.K.Moorthy | Vice-Chairman [email protected]

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The Masterbuilder - March 2011 · www.masterbuilder.co.in

Loya Constructions Pvt. Ltd

Contents

Formwork: Industry Analysis

Formwork Equipment:Policy Initiatives Hold the Key for Continued Growth of Formwork Industry

162

M.K. Prabhakar, Associate Editor

28

Budget 2012-13: Analysis Budget 2012-13 Impact on Infrastructure Sector

40

Automation and Robotics Automation and Robotics in Construction: Applications, Advancements and Challenges

A Masterbuilder Bureau Report

Chaitanya Goyal

48

Ground Engineering: Structural Failure Non-compliant Building in New Zealand Meets a Fatal End

54

Urban Engineering: Computational Tools Computational Tools Applied to Urban Engineering

66

Urban Engineering: Traffic Management 'Intelligent Traffic Management Systems: A Growing Necessity

72

Sustainable: Infrastructure The Beijing Bohai Innovation City

Benefits of BIM Technology in Reinforced Concrete Industry

92

Concrete: Benefits Concrete VS Asphalt Battle for the Future Choice of Construction Material

94

Concrete: Durability Mechanisms of Deterioration of Reinforced Concrete Structures

106 118

Bhavani Balakrishna

140

Manideep Saha, Head, AEC & Geospatial, Autodesk India

152

'IT' Providing an Impetus for the Surveying Industry

48

28 40 The Masterbuilder - March 2012 · www.masterbuilder.co.in

George Sergi, Ph.D, Technical Director, Vector Corrosion Technologies

Concrete Corrosion: Reinforcing Steel Recent Developments in Mitigation of Rebar Corrosion in Concrete

Corrosion: Repair & Rehabilitation Repair Principles for Corrosion Damaged Reinforced Concrete Structures

Concrete: Repair & Rehabilitation Repair and Rehabilitation of Corrosion Damaged Concrete Structures

P. Srinivasan, Principal Scientist, ACTEL, CSIR- Structural Engineering Research Centre , CSIR Campus, Taramani

Communication: Feature URCIMSTM – En-Route to a Systematic Future

86

Corrosion: Reinforcing Steel Corrosion of Steel in Concrete & Assessment Techniques

MG Alexander and JR Mackechnie, Department of Civil Engineering, University of Cape Town

Urban Engineering: BIM Sustainable Design Analysis and Building Information Modeling

84

Dr. Manu Santhanam, Associate Professor, Department of Civil Engineering, IIT Madras

M N Ramesh, CEO, Savcor India Private Limited

124

MB Report

76

12

88

Bhavani Balakrishna

Armando Carlos de Pina Filho, Fernando Rodrigues Lima, Renato Dias Calado do Amaral Federal University of Rio de Janeiro (UFRJ), Brazil

Editor's Comment.................8 & 10 News & Events............................20 E-Scape.....................................252 Advertisers Index........................16 Classification Index.....................18

Communication: Feature Comprehensive Guidelines for Execution of Epoxy/PU Floorings - Part II

66

H & K Rolling Mill Engineers Pvt.Ltd

Contents

Resistant: Infrastructure 156 Quake Unraveling the Secrets of 'Tokyo Sky Tree'

Infrastructure: Tunnels 220 The Gotthard Tunnel Pass: A True Tunneling Marvel

Bhavani Balakrishna

Bhavani Balakrishna

Failure 168 Formwork: Formwork Failure: Cases & causes

Infrastructure Tunnels 226 Marol Maroshi Tunnel: Quenching Mumbai's Thirst

Special Correspondent

Bhavani Balakrishna

: Formwork 174 Focus Modern Formwork Systems: A Ringside view of the Variety of Formwork Systems Available Today

Success in Hot Aggressive Climates

M.K. Prabhakar, Associate Editor

Fabric Formwork 180 Focus: Fabric Formwork: Sky’s the Limit

and Convey: The Only Answer to Tackle 231 Crush Present Day Surface Mine Economics

Special Correspondent

188

Tunnelling: Construction Chemicals The Influence of Construction Chemicals on Tunnel Durability Willie Kay, Managing Director of WAK Consultants Pte Ltd / WAK Technologies Pte Ltd , MC Bauchemie Muller GmbH & Co

Growth in India

Bhavani Balakrishna

210

Conversation with Mr.Ajay Maini, Director, 234 InMaini Construction Equipment

235 'Next - Gen' Fiberglass Shuttering Systems from Indigo

Engineernig: TBM's 194 Tunnel Modern TBMs: Enabling the Next Wave of Infrastructure

204

Feature 228 Communication: Stirling Lloyd Maintains Cut and Cover Tunnel

236 Making a Mark with Modular Tunnel Formwork Systems Chemicals: International Conference 238 Construction C3 Catapults CCMA into National Limelight MB Bureau Report

Tunnel Engineering: Repair & Rehabilitation Tunnel Repair and Rehabilitation Using Shotcrete Special Correspondent

Stimulus 2012 246 Events: UltraTech 'Stimulus 2012' MB Bureau Report

Tunnel Engineering: Concrete Admixtures Durable Concrete for Tunneling Applications Eugenkleen, MC - Bauchemie Mueller GmbH and Co. KG

Feature 250 Communication: Revolutionary Solutions for Concrete Repair

Chemicals 216 Construction: Construction Chemical Industry in India 'vision 2020'

Dr. SK Manjrekar, Managing Director, Sunanda Specialty Coatings Pvt. ltd.

251 Intelligent Shutters from Gandhi Automations

194 174 Cover Picture Courtesy: www.rmdkwikformnews.co.uk

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216 226

Singh Construction Equipments

Contents

Advertisers Index A

I

Action Construction Equipment Ltd

123

IBK Media

215

Ambattur Scafolding Company

187

Igloo Tiles

71

Atul Fasteners Ltd

117

Indigo Multitrade Pvt.Ltd

159

INSTRUCT

225

B Baicon 2012

237

Bajaj Products

223

C Case New Holland Construction Equipment (India) Pvt.Ltd

23

Cerachem Pvt.Ltd

35

Chetra Machinery India Pvt.Ltd

25

Chowgule Construction Technologies Pvt.Ltd

JB Engineering and Industrial Company

213

JBA Concerete Solutions

129

L Larsen & Toubro Ltd

43

Lipi Polymers Pvt.Ltd

57

Loya Constructions Pvt.Ltd

11

Back Cover

Cosmos Construction Machineries & Equipments Pvt.Ltd

173

Cosmos Sales Corporation

177

Credence Engineers Pvt.Ltd

213

D DCS Trading & Services Pvt.Ltd

93

Dextra India Pvt. Ltd

227

Doka India Pvt. Ltd

21

E Esquire CMAC Pvt.Ltd

105

E-Surveying Sofetech (India) Pvt.Ltd

209

F Fayat Group

7

G Gandhi Automations Pvt.Ltd

M Machines & Engineering Company

6

H H & K Rolling Mill Engineers Pvt.Ltd

161

Maruti Steel Fab

167

MC Bauchemie Pvt.Ltd

61

Metal Tech Constructions Pvt.Ltd

87

Metecno India Pvt.Ltd

Front inner (2)

MM Castings (P) Ltd

219

MRT Chemicals Pvt.Ltd

223

N National conference on Fast Track Road Construction in India

2nd Wrapper


Front inner (1) / 53

Hyundai Construction Equipment India Pvt.Ltd

5

215

Nav Nirman Beam Technics

17

Nawa Engineers & Consultants Pvt.Ltd

89

Neocrete Technologies Pvt.Ltd

83

Nina Concrete Systems Pvt.Ltd

151

P Back inner

R

13

Hess Concrete Machinery India (P) Ltd

19

Maini Construction Equipment Pvt.Ltd

Pidilite Industries Ltd

Reliance Industries Ltd

193

Relyon Facility Services Pvt.Ltd

229

Robbins Tunneling & Trenchless Technology (I) Pvt.Ltd

145


201

Roof India

233

Roshanlal Jain & Sons (Roljack Industries)

203

ROTHO - Robert Thomas Metall- and Elektrowerke GmbH & Co. KG

223

S Savcor India Pvt.Ltd

81

Schwing Stetter (India) Pvt. Ltd

51

Sika India Pvt.Ltd

155

Singh Construction Equipments

15

Sleek Boards (India) Ltd

33

Speedcrafts Ltd

139

Sreerama Industries

229

STA Flooring (Sanjay Tekale Associates)

69 / 115

STP Ltd

121

MahindraGenio

9

Greaves Cotton Ltd

16

J

Rockster India Ltd

101

T Tac System Formwork Sdn Bhd

181

Technocraft Group

165

Tekla India Pvt.Ltd

79

Texsa India Ltd The Masterbuilder Subscription Form The Supreme Industries Ltd Toshniwal Systems & Instruments Pvt.Ltd

27 249 37 197

U Unipave Engineering Products

135

Unisteel Engineering Works

65

United Steel & Structurals Pvt. Ltd

97

Universal Construction Machinery & Equipment Ltd

91

URC Infotec Pvt.Ltd

73

V Venus Equipments & Tools Pvt.Ltd VRVR Constructions

29 / 31 209

W Wirtgen India Pvt.Ltd

47

Z Zamil Steel Buildings India Pvt.Ltd

109


Contents

Advertisers Index / Classification AAC

Formwork

Hyderabad Industries Limited

Bajaj Products

223

Metecno India Pvt. Ltd.

Building Materials


177

United Steel and Structurals Pvt Ltd

97

MRT Chemicals Pvt Ltd

DOKA India Pvt Ltd

21

Zamil Steel Buildings India Pvt. Ltd.

109

Front Inner (1) / 53 223

Loya Peb

Concrete Block Making Machinery

Indigo Multitrade Pvt Ltd

159

Roofing Fastners

Hess Concrete Machinery India Pvt Ltd 2nd Wrapper

Maini Construction Equipment Pvt Ltd

161

Atul Fasteners Ltd

Machines & Engineering Company (MEC)

Maruti Steel Fab

167

Scaffolding

121

Concrete demolishing


VRVR Construction

Sreerama

209

Construction Equipment & Machinery

Facility Services

Action Construction Equipment Ltd.

Relyon Facility Services Pvt. Ltd.

123

Case New Holland Equipment Pvt Ltd Chetra Machinery India Pvt. Ltd. Cosmos Construction Machineries & Equipments Pvt.Ltd DCS Trading & Services Pvt Ltd

23

Flooring

25

JBA Concrete Solutions

173


93

Esquire CMAC Pvt.Ltd

105

Hyundai Construction Equipment India Pvt. Ltd.

5

JB Engineering And Industrial Co

213

Marini India Pvt Ltd. (Fayat India)

7

Schwing Stetter India Pvt. Ltd. Singh Construction Equipments & Machinery Pvt. Ltd. Unipave Engineering Products

51 15 135

Universal Construction Machinery & Equipment Ltd.

91

Venus Equipments And Tools Pvt Ltd

29 / 31

17 229 229 129

Neocrete Technologies Pvt Ltd

83 183

STA Concrete Flooring Solutions

69 / 115

Green Building Products Hyderabad Industries Limited

Front Inner (1) / 53

OEM Suppliers MM Castings Pvt. Ltd.

219

PEB Loya Peb Metecno India Pvt. Ltd.

11 Front Inner (2)

United Steel and Structurals Pvt Ltd

97

Zamil Steel Buildings India Pvt. Ltd.

109


65

Repair and Rehabilation

Cranes Action Construction Equipment Ltd. DCS Trading & Services Pvt Ltd

Cera - Chem Pvt. Ltd 123 93

Crushing

Chowgule Construction Technologies Credence Engineers Pvt Ltd Dr. Fixit (Pidilite)

35 Back Cover 213 Back Inner

Kormann Rockstar Recycler India Pvt.Ltd

201

Mc Bauchemie (India) Pvt. Ltd.

61

Nawa Engineers & Consultants Pvt Ltd.

89

Nina Concrete Systems Pvt Ltd

151

Sika India Pvt.Ltd

155

STP Ltd

101

Roshan Lal Jain & Sons (Roljack Industries)

203

Doors Automatic Gandhi Automations Pvt.Ltd

9

ECC

18

The Supreme Industries Ltd.

37

Roofing

L & T Construction

43

Bajaj Products

223

Maini Construction Equipment Pvt Ltd

161

Maruti Steel Fab

167

Sreerama

229

Software Solutions E Surveying Softech (Indias) Pvt. Ltd.

Lipi Polymers Pvt. Ltd.


57

109

Tekla India Pvt LTD.

79

URCIMS

73

Splicing Systems Dextra India Pvt. Ltd

227

Tiles Manufacturers Igloo Tiles

71

TMT-Technology Suppliers H & K Rolling Mill Engineers Pvt.Ltd

13

Tunnel Boring Machine Robbins Tunneling & Trenchless Technology (I) Pvt. Ltd. Waterproofing

47

117 187

Cera - Chem Pvt. Ltd

Wirtgen India

Front Inner (2)

Ambattur Scaffolding Company

Precast Concrete Rotho(Robert Thomas Metall- und Elektrowerke GmbH & Co. KG) 223

11

Chowgule Construction Technologies Credence Engineers Pvt Ltd Dr. Fixit (Pidilite)

145 35 Back Cover 213 Back Inner

Mc Bauchemie (India) Pvt. Ltd.

61

Nina Concrete Systems Pvt Ltd

151

Sika India Pvt.Ltd

155

STP Ltd

101

The Supreme Industries Ltd.

37

Texsa

27

Waterproofing-Tunnel Nina Concrete Systems Pvt Ltd

151

Sika India Pvt.Ltd

155

MahindraGenio

News & Events

CONSTRUCTION EQUIPMENT Exception from Import Duty for Road Equipments and TBM's

space. In total, 300,000 square meters of space are available for bauma China 2012. Interest from the industry worldwide continues at a high level: Austria, Finland, Germany, Great Britain, Italy, Korea, Spain and the US will each be taking a pavilion at bauma China.

Natural Gas Could Soon Fuel Construction Equipments

Full exemption from import duty on specified equipment imported for road construction by contractors of Ministry of Road Transport and Highways, NHAI and State Governments is being extended to contracts awarded by Metropolitan Development Authorities. Tunnel boring machines and parts for

Record Number of Exhibitors at bauma China 2012

The buzz around bauma China is getting bigger by the day. Already bauma China is setting a new exhibitor record: By the middle of February 2012, over 1,900 companies had already applied to exhibit at the International Trade Fair for Construction Machinery, Building Material Machines, Construction Vehicles, and Equipment, which takes place in November 2012. This figure exceeds the figure of 1,892 exhib-

20

their assembly are covered by this exemption. The Union Finance Minister, Mr.Mukherjee proposed to allow their import free of duty without enduse condition, in the Union Budget 2012-13. The pace of awarding of road and highway projects is expected to pick up steam in the next few months.

itors who took part in the last bauma China. And we still have nine months to go before bauma China 2012 gets under way: it is to be held between November 27 and 30, 2012 at the Shanghai New International Expo Centre (SNIEC). Mr.Collin Davis, Exhibition Group Director at Messe München International, commenting on the development said "It was our aim to offer our exhibitors improved conditions for their presentations in the halls. And, as we have eight more halls available for this year's event, we have been much better able to meet their space requirements." Demand for space on the open-air site far currently exceeds the space available. Important key players, however, are making use of the additional hall


Tougher emission norms have become the norm, throughout the world and India is no different. Construction equipment suppliers are therefore going the whole hog literally to come out with products that less polluting and more importantly also fuel efficient, a key factor affecting sales in a country like India. There are already several research initiatives that are focused on coming out with alternate sources of fuel for powering construction equipment. Haulage trucks that are powered by liquefied petroleum gas or LPG is a good example. There are also reports of hybrid haulage vehicles on the line of cars that could hit the market soon. A lot of R & D focus of major construction equipment suppliers of late has been focused on improving engine performance, which bodes well ultimately for the customer. It however, remains to be seen as to how the suppliers manage to offer technologically advanced, fuel efficient and environment-friendly machines, while at the same time keeping their prices competitive.

Doka India Pvt. Ltd

News & Events

INFRASTRUCTURE Expert Panel says PPP not a Good Idea

URBAN INFRASTRUCTURE

38 New BRTs Proposed for Delhi

The Delhi government has planned 38 new corridors, with 14 already sanctioned of Bus Rapid Transit (BRT). In 2011, it decided to rename BRT as integrated transit corridor, probably to make Delhiites forget their regular plight on the Ambedkar Nagar-Moolchand BRT, known for its jams and lengthysignal cycles. Six corridors have been handed over to the DIMTS (Delhi integrated multimodal transit system) which is responsible for maintaining BRTs. DIMTS will apply the same design constituting a central bus lane with MV (motor vehicle) lanes on either side. The remaining part of the road is to be retrofitted according to the guidelines of UTTIPEC (Umbrella Traffic and Transport Agency).The design also includes separate parking spaces for Gramin Sewa and autorickshaws, apart from hawker spaces close to intersections. According to DIMTS, it has adopted a hybrid system considering the congestion in the areas, so that the separate bus lane can merge with the mixed traffic on narrow stretches. Prof P K Sarkar, a transport planning expert, said that the design does not use space optimally, and the main problem is in the junction treatment involving lengthy signal cycles. He added that the corridor could work if the bus lane is totally separated or elevated, as traffic jams are unavoidable in a traffic-heavy junction with a bus lane at grade with an MV lane.

22

While there have been calls from several quarters for increasing the focus on public-private partnership (PPP) model for infrastructure development, an expert panel has said something to the contrary. A planning commission working group, headed by former Managing Director of Delhi Metro, Dr.E.Sreedharan has rejected the PPP model for developing urban infrastructure projects, particularly transport infrastructure, according to a recent news report. The group also pointed out that internationally too the PPP model has not been successful, particularly in the case of urban infrastructure projects. It however remains to be seen how seriously the government takes the panel's recommendations, provided the fact that it has been banking on huge private sector participation for furthering the infrastructure development process in the country.

Mega Infrastructure Projects Expected to Reach Completion by 2013

The Maharashtra state government has allocated funds to the tune of ` 4,825 crore for the MMRDA (Mumbai Metro-


politan Region Development Authority) to complete mega-infrastructure projects in and around Mumbai in the fiscal year 2012-13. Informing that no new announcements have been made, Rahul Asthana, the MMRDA Commissioner stated that the goal is to complete mega-projects. The budget was sanctioned recently at the MMRDA's 130th meeting chaired by the Chief Minister Prithviraj Chavan. The 22-km Mumbai-Trans Harbor Link would be started at an estimated cost of ` 8,800 to be spent through 4 to 5 years. The 126-km Virar-Alibag Multi-Modal Corridor will be implemented at a cost of ` 9,326 crore. Involving two phases namely, the 79-km Virar-Chirner and 47km Chirner-Alibaug, it will emphasize on separate lanes for buses, two-wheelers and non-motorized transportation, said the IANS news report. The ` 338 crore allocated for the Metro rail will cover the Versova-Andheri-Ghatkopar stretch, the Charkop-Bandra-Mankhurd segment and the underground ColabaBKC-Andheri Link. The monorail has been allocated with ` 870 crore, while the road network around the city will be developed at a cost of ` 1,460 crore. The suburban railway network, which is the lifeline of Mumbai, will be developed at a cost of ` 290 crore, and the satellite towns around Mumbai have been allotted ` 800 crore. The MMRDA has also allotted ` 390 crore to expand water resources, taking into account the increasing water requirements in the Mumbai Metropolitan Region.

Standard & Poor Explores the Risks Involved in Indian Infrastructure Projects A recent Standard & Poor's (S&P) rating states that Indian infrastructure projects are likely to be affected by the airport regulator's decision to put forth a tariffincrease proposal for Delhi international airports. The decision can hold back private-sector participation in regulated high-investment projects.

Case New Holland Construction Equipment (India) Pvt.Ltd

News & Events

INFRASTRUCTURE

Mr.Rajiv Vishwanathan, the credit analyst of S&P was quoted stating that the potential rise in tariffs at Delhi airport stresses the requirement for a privatepublic participation policy at every level of the government. He explained that private funding can be sought by building confidence with regard to several factors like proper project preparation, feasibility study, transparent bidding and so on. An impact of the tariff-rise on airlines and passengers was also mentioned apart from the reasons behind the demand of higher tariffs at the Delhi airport. It further describes the effect brought upon the project sponsor due to tariff-adjustment delays. Private sector participants will observe the consequences, transparency and timeframe for the regulatory process. Mr Vishwanathan opined that higher tariffs can have a negative impact on a few low-cost airlines functioning outside Delhi, and stated that large international airlines could bring down the frequency of flights, rather than stopping operations to Delhi or shifting to low-cost airports.

Abhiyan”. Addressing a group of liberated manual scavengers during his visit to Sulabh headquarters here, he said that the government is considering increasing the grant of ` 3 thousand to ` 7-8 thousands for the construction of individual toilets in rural areas. The minister said that his ministry would focus on the implementation of sanitation related issues at gram panchayat level. He announced to open a “sanitation club” for each and every school of the country and the ministry will provide an annual grant of ` 3000 for every sanitation club to create awareness among children at grass root level.

least one lakh toilets in rural areas to achieve total sanitation cover in next ten years. He requested Dr. Pathak to come forward to support government's aim in this regard.

Appreciating the efforts of Sulabh International in the field of Sanitation, M r. R a m e s h u r g e d i t s f o u n d e r Dr. Bindeshwar Pathak to focus on rural areas to achieve the target of total sanitation in the country. Lauding the initiative of Sulabh, the minister said that there is a need of the construction of at

Expressing great concern over the issue of open defecation in India, the Minister pointed out that country still lacks in the field of sanitation. He called upon NGOs to launch awareness campaigns to motivate for use of toilets instead of going for open defecation, further added the release.

AIR PORTS

First Private Airport in the Country to be Built at Karaikal

Rural Development Ministry proposes 40% increase in sanitation projects The Union government is seriously considering to 40 percent increase for sanitation sector in the annual budget this year, according to a recent press release from the Union Ministry of Rural Development. Indicating this Union minister for Rural Development, Mr. Jairam Ramesh announced to launch a nationwide sanitation campaign with title “Nirmal Bharat

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The country's first fully private airport would become a reality in another two years time. The airport would come up near Karaikal, in Puducherry, stated the developers, a Coimbatorebased consortium, Super Airport Infrastructure Pvt, making it a rare first in the country. The airport could boost tourism in the region which has several spiritual centers dotting nearby towns. The airport is also


expected to give boost to further economic development of the region, along with the nearby port in Karaikal. According to the Chairman of the c o m p a n y, M r. J . V e n k a t e s a m Chowdhury, the project would be spread over an area of 562 acrea, with the initial expense involved will be `150 crore.

Chetra Machinery India Pvt.Ltd

News & Events

CORPORATE Tata Power with SN Power plan to buy major stake in Sikkim's Sarda Energy project

of quakes in north India is still high with Sikkim and most of north India coming under seismic zones 4 and 5, viz. high vulnerability to high-intensity earthquakes.(picture courtesy: Chip Chipman/Bloomberg)

Rural Electrification Corp. Ltd to avail a new loan of €100 million from KfW Bankengruppe The consortium of Tata Power Co. Ltd and SN Power group that was formed in 2009 is holding discussions about a Rs 200 crore transaction to buy a sizeable stake in the 96 MW hydroelectric power project from Sarda Energy and Minerals, Sikkim, according to reports. Sarda Energy has appointed Deloitte Touche Tohmatsu India Pvt. Ltd for advice on the stake sale. According to Tata Power's website, the consortium was formed to jointly carry out hydroelectric development plans in India and Nepal. Currently involved in Himachal Pradesh's 236 MW-Dugar hydroelectric projects, and Nepal's 880 MW-Tamakoshi-III project, the consortium aims at launching 2000 MW with construction underway or operational by 2015, and an aggregate of 4000 MW by 2020. A Sarda Energy spokesperson stated that the equity amount to be divested by the company will be fixed after discussions, as the project is in the preliminary phase and the company is looking for investors. The power sector of India requires an additional investment of $400 billion in the 12th Five Year Plan, with fund scarcity endangering to deteriorate the current energy deficit, which is the chief stumbling block to sustain and further economic development. Hydropower projects require dedicated technology and design, and are vulnerable to geological disasters like earthquakes, landslides, and floods. The 6.8 magnitude quake that struck the Sikkim-Nepal border last September has raised concerns over the future of hydroelectric development in the country. Scientists predict that the probability

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water by 2015, and 15 percent by 2020. India's top power-sector regulator namely, Central Electricity Regulatory Commission has put forth guidelines to issue renewable energy certificates in a bid to encourage green energy. States, individuals and trading entities can buy green energy from certificate holders. Different levels of purchase obligations will be apportioned to different states, but the high production costs and impact on the budgets of power utilities are likely to cause dissuasion.(Picture Courtesy: http://www.sarkaritel.com)

Japan's Kobe Steel acquires 3.25 percent stake in Man Industries (India) Ltd

The REC (Rural Electrification Corp. Ltd), a state-owned corporation is raising a €100 million-loan from Germany-based KfW Bankengruppe to fund renewable energy projects at concessional interest rates. The REC Chairman & MD, Mr. Rajeev Sharma said that the process is almost done with the loan agreement to be signed soon, and a spokesperson from KfW Bankengruppe confirmed the sanction, stating that the contract will be signed this month. REC has already availed a €140 million loan for power transmission and distribution projects. It has sought a foreign lender to overcome the acute funds shortage in power companies in India. Together with PFC (Power Finance Corp. Ltd), REC accounts for about 60 percent of financing for the power sector. This is the first time that REC has set forth guidelines for financing renewable energy projects, given the current scenario that demands diverse energy sources, forcing the need for alternative renewable sources. According to the climate-change action plan, India must generate 10 percent of its power from renewable sources like solar, wind and


Japan's Kobe steel is set to buy 3.25 percent stake in the Mumbai-based Man Industries (India) Ltd, a steel pipe manufacturing company. The investment is calculated at ` 30 crore and the duo have planned to survey the prospects in the global market, as part of the transaction. A report from Man Industries states that the companies will carry on with their research to strengthen their 'strategic' partnership on a long-term basis. Kobe intends to pick up 1.81 million shares at ` 165 per unit. Man Industries showed a 17 percent rise in revenues and a 4.7 percent rise in the net profit for FY12's first nine months. According to Mr.R.C. Mansukhani, the promoter and chairman of Man Industries stated that it is the first such alliance, where a plate/coil manufacturer from Japan has associated with a pipe manufacturer based in India. (Picture Courtesy: Kobe Steel)

Texsa India Ltd

Budget 2012-13 Analysis

BUDGET 2 12-13

IMPACT ON INFRASTRUCTURE sector A Masterbuilder Bureau Report

T

he Union Finance Minister Mr.Pranab Mukherjee's budget speech for 2012-13 was punctuated by bits of dry humour in between. A good example was when the seasoned politician stated that being the Finance Minister of the country was one of the most difficult jobs. In a way, the Finance Minister was speaking the truth since he had the onerous task of balancing populism with a crying need for reforms. The budget was focused on trimming down subsidies to two percent of the GDP and left India Inc with mixed feelings. Terming 2011 as the “year of recovery interrupted”, the Mr.Pranab Mukherjee stated that the current year was a challenge for Indian economy but India has thrived under such challenges and will continue to do so. He said that the aim of his budget is to create an enabling atmosphere for corporate entities, farmers, entrepreneurs, and workers to take initiatives for robust growth. He further said that the budget also aims to ensure that the benefits of growth reach all sections of population. As expected, focus on infrastructure development was one of the key components of the Union Budget 2012-13. While several measures to rejuvenate the infrastructure development process through infusion of fresh funding sources has been made, there were several other areas where the pressure of coalition politics and the recent set back in elections in some states seemed to have clearly weighed heavily on the Centre, stopping them from taking bold reform initiatives. Let us take a look at some of the highlights of the Union Budget 2012-13 and its impact on the infrastructure and real estate sectors.

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Venus Equipments & Tools Pvt.Ltd


Mixed bag: The Union Budget 2012-13 was neither outright populist nor reformist

Sector Empowered Emphasizing on infrastructure and industrial development, the Finance Minister said that during the 12th Plan, infrastructure investment will go up to ` 50 lakh crorewith half of this expected from private sector. Stating that in 2011-12 tax free bonds for ` 30,000 crore were announced for financing infrastructure projects, he proposed to double it to raise ` 60,000 crore in 2012-13. The Minister proposed to allow External Commercial Borrowings (ECB) to part finance Rupee debt of existing power projects. The coal shortage issue which has been plaguing the power sector has been addressed , at least temporarily through the customs relief for fuel for thermal power projects that has been announced under the budget. In the realm of infrastructure, customs relief is being given to power, coal and railways sectors. While coal gets full

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customs duty exemption for 2 years, natural gas, LNG and certain uranium fuel get full duty exemption this year. Different levels of duty concessions are being provided to help mining, railways, roads, civil aviation, manufacturing, health and nutrition and environment. The budget was though silent on the duty levied on imported power equipment. Those who were waiting for policy initiatives aimed at attracting overseas power equipment companies to set up shop in India also need to wait since no such initiatives were announced. In a move aimed at giving further fillip to the renewable energy sector, solar thermal plant imports have been given customs duty exemption. The Road to Growth The allocation for the Ministry of Road Transport & Highways has been enhanced to ` 25,360 crore, in 2012-13 which is a 14% hike from the previous allocation. The Finance Minister in the


budget proposed to allow External Commercial Borrowings (ECB) for capital expenditure on the maintenance and operation of tolled roads and highways, as long as it is part of the original project. This is with a view to encourage PPPs in the road sector, according to the Finance Minister. The Finance Minister said that a target of 8,800 km for the highways to be constructed under the NHDP has been set during 2012-13. He stated that the Ministry of Road Transport & Highways is geared up to achieve the target of awarding projects for 7,300 km under NHDP during 2011-12. This would be 44% higher than the figure of 5,082 km awarded during 2010-11. The Finance Minister informed that out of the 44 projects awarded during 2011-12, 24 projects have fetched a premium. The allocation for Pradhan Mantri Road SadakYojana (PMGSY) has been proposed to be increased by 20 per cent to ` 24,000 crore in 2012-13.

Venus Equipments & Tools Pvt.Ltd


The hike in allocation is likely to see a renewed impetus as far as awarding and building of major highway projects and expressways in the near future. A Smooth Ride The government has bought some cheer to the urban infrastructure planners, with the Urban Development Ministry getting an increase of Rs.874 crore in its annual budget. A significant chunk of the amount is expected to be spent on developing the metro networks around the country. The ministry's allocation last year was ` 6,855 crore which has been now increased to ` 7,729 crore. The increased allocation is expected to expedite project completion processes in metro projects in the near future by the ministry. Not Grounded While no dramatic measures were announced for improving civil aviation infrastructure during the Union Budget 2012-13, a slew of steps to improve cash flow in order to bring back airline carriers on the right track hold promise. While airline carriers can now get cheaper dollar loans through ECB, the Finance Minister also announced that the step to allow 49% stake for foreign airlines in Indian carriers and direct import of aviation turbine fuel (ATF), measures that could improve the situation for airline carriers and in turn

put pressure on improving airport infrastructure in Indian cities. This apart, the stimulus package announced as part of the budget for the infrastructure sector is expected to have a positive impact, as far as development of civil aviation infrastructure is concerned. It remains to be seen as to what are the other policy initiatives that the government brings into address issues such as land acquisition and granting of environmental clearances for civil aviation infrastructure projects. Status Quo The port sector looks set for a long haul with no major policy initiatives announced pertaining to its development in the Union Budget 2012-13. However, a significant chunk of the ` 50 lakh crore investment that has been announced for the infrastructure sector during the 12th Plan period is expected to flow into the ports sector, which with the boost to manufacturing, is automatically expected to play a key role in the next five years. Manufacturing Thrust The lack of clarify on the implementation of the Direct Tax Code (DTC) means that the situation with respect to investment in Special Economic Zones (SEZs) is likely to be uncertain for some more time. There are however indications

The power sector has got much needed funding in Union Budget 2012-13

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that the manufacturing sector would continue to get attention on a priority basis, which could prove a boon to project developers. The Finance Minister for example, has announced to reduce basic customs duties on plant and machinery imported for setting-up of iron ore pellet plants or iron ore beneficiation plants from 7.5 percent to 2.5 percent. Mr.Mukherjee said that relief has been proposed for sectors such as steel, textiles, branded readymade garments, low-cost medical devices, labour intensive sectors producing items of mass consumption and matches produced by semimechanized units. He proposed to fully exempt automatic shuttle-less looms from basic customs duty of 5 per cent. Similarly, full exemption on basic duty is being accorded to automatic silk reeling and processing machinery as well as its parts, measures which could give much needed impetus to the textile sector and in turn impact the fortunes of project developers. Adding to the manufacturing sector focus is the announcement on the Delhi-Mumbai Industrial Corridor by the Finance Minister. Mr.Mukherjee informed that the Japanese Prime Minister has announced US $ 4.5 billion for the Delhi-Mumbai Industrial Corridor (DMIC). In September last year, the Government approved Central assistance to the tune of ` 18,500 crore

Sleek Boards (India) Ltd


for a period of five years for the project, the Minister added. The DMIC is being developed on either side of the Western Dedicated Rail Freight Corridor. Rural Tilt There was also a distinct tilt towards rural development in the Union Budget 2012-13, with the announcement of enhancing allocation under the Rural Infrastructure Development Fund to ` 20,000 crore with ` 5,000 crore exclusively earmarked for creating warehousing facilities. Similarly, Viability Gap Funding (VGF) under the Scheme for Support to PPP in infrastructure has been extended to irrigation including, channels, embankments and dams, which comes as much needed good news for project developers. Ensuring Investment Flow The government has realizing the importance of the infrastructure sector s the driver of economic growth had recently approved a harmonized master list of infrastructure sector. The move is aimed at removing ambiguity with respect to defining sectors that fall under the infrastructure sector and improve the investment climate in the sector. The Finance Minister in his

A proposal to develop and maintain railway stations on the lines of airports has been announced in the Railway Budget 2012-13

budget speech highlighted how the Indian Infrastructure Finance Company Limited (IIFCL) has been set up to improve ease of access to credit to infrastructure projects. The government has also announced a proposal to introduce a new scheme called Rajiv Gandhi Equity Savings Scheme to allow for income tax deduction of 50 per cent to new retail investors who invest up to ` 50,000 directly in equities

and whose annual income is below ` 10 lakh. Regarding capital markets, the Finance Minister proposed to allow Qualified Foreign Investors (QFIs) to access Indian Corporate Bond market. He also proposed simplifying the process of Initial Public Offer (IPO), all measures that are likely to have a positive impact on the investment climate with respect to infrastructure projects in the country. The increased flow of investment, apart from the other policy initiatives that have been proposed as part of the Union Budget will also play a role in deciding how the next phase of urban infrastructure development initiatives pan out in the near future. Chugging Along

Economic turnaround of airline carriers and increased flow of investment into infrastructure is expected to give push to airport projects

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The political drama that was witnessed after the announcement of the Railway Budget 2012-13 perhaps completely overshadowed the fact that it was the first time in several years that passenger fares had been hiked, however marginal, a fact which made it a different budget, in more ways than one. In this Budget, the Railway Minister has focused on five important fields, which are: Safety; Consolidation; Decongestion & Capacity Augmentation; Modernization; and to bring down the

Cerachem Pvt.Ltd


Operating Ratio from 95% to 84.9% in 2012-13. Proposing highest ever plan outlay for the Railway Budget, the Railway Minister. Mr. Dinesh Trivedi, in his budget speech said that it will be financed through Gross Budgetary Support (GBS) of ` 24,000 crore; Railway Safety Fund of ` 2,000 crore; internal resources of ` 18,050 crore; and Extra Budgetary Resources of ` 16,050 crore, which includes market borrowing of ` 15,000 crore through IRFC. One of the highlights is the proposal to set up the Indian Railways Stations Development Corp, to maintain and develop stations on the lines of airports. Another eagerly awaited development that has left many disappointed is in the sphere of high speed trains. The minister has announced the setting up of a National High Speed Rail Authority and the addition to the pre-feasibility studies to the already six high speed corridors that have been identified. The Delhi-Jaipur-Ajmer-Jodhpur line will be taken up for study in 2012-13. The minister has announced a rail coach factory at Palakkad, apart from other coach manufacturing facilities in Kolar in Karnataka and Kutch in Gujarat. A wagon factory in Sitapali, in Odisha has also been announced. A new component factory would be established at Shyamnagar in West Bengal. Safety was the buzzword in the minister's budget speech. He announced the setting up of an independent Railway Safety Authority and that all unmanned level crossings in the country would be abolished in the next five years time. Another positive move has been the announcement during the Railway Budget 2012-13 of setting up of renewable energy capacities by the Railways for its own use. The move if implemented in all earnestness could prove to be a trendsetting one, worthy of emulation by other sectors. It however, remains to be seen as to whether the overall package announced as part of the Union Budget to 2012-13 to rejuvenate the infrastructure sector has a positive impact on the railways.

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Win some, lose some: the Union Budget has brought some cheer to the realty sector

The Realty Scene For those in the real estate sector, the Union Budget 2012-13 was among the most eagerly awaited ones in recent times. Ultimately the announcements of the Finance Minister turned out to be a mixed bag for those in the sector. For those hoping for interventions such as award of infrastructure status to realty and increase in income tax exemption on principal and interest, were left disappointed, as the budget kept silent on these key issues. Grant of infrastructure status has been a long pending demand, since the sector is a known driver of economic growth and generates thousands of jobs across the country. However, there was a silver lining in the form of the extension of the 1% interest rate subvention loans up to ` 15 lacs for housing projects up to ` 25 lacs by 1 more year. External Commercial Borrowings (ECBs) for affordable housing is another move that is expected to boost the sagging fortunes of the realty sector. Similarly the setting up of a Credit Guarantee Trust fund for ensuring institutional credit for housing loans is another measure that is expected to


bring some cheer to buyers. The hike in indirect taxes though is expected to put a spanner again into the smooth delivery of real estate and could impact demand in the long run. The government has also stated that it is committed in its efforts to arrive at a broad based consensus on the issue of FDI in retail, is another hope amidst the gloom for the realty sector. The real estate sector was in immediate need of support measures through means of policy stimuli and easing of liquidity, tax concessions and the development of a transparent regulatory mechanism, steps that could have lead to significant spurt in demand, especially in urban agglomerations. No specific policy initiatives were announced for attracting more FDI into the realty sector in the budget. It was felt that the easing of norms pertaining to investment and exit from projects would have helped in reviving the interest of overseas players in the Indian real estate market. Picture Courtesy Thebigprojectme.com, Situanafro.com Mumbai-localtrains.com, Wikipedia.org Twocircles.net

The Supreme Industries Ltd

Automation and Robotics

Automation and Robotics in Construction: Applications, Advancements and Challenges Chaitanya Goyal

R

ecent advancements in the construction industry have helped us analyze the importance of time bound progress, productivity, safety, quality and skilled labor availability for profitable and successful construction. Among the various phases of structure formation from site survey to its completion, the construction phase is

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of paramount importance and efficiency in the same lays the foundation for a fruitful and quality project. It is when the construction manager's worst nightmares are about to come true, that the automation and robotics technology synchronizes with an engineer's and a manager's needs and comes to their rescue!


The advent of computer science and evolution of electronics and robotics proved to be a milestone in the history of mankind. Computer technology applications in construction changed the very face of the industry. The eighties witnessed introduction of robotics and automation in construction for the prefabrication of components and


addressing large-scale and complicated field problems and humanoid robotic technology is being developed for construction site and building service application.

Picture Source: Husqvarna Social Media News Room

Analyzing the need of automation and robotics in construction industry

houses, with the world's first robot developed in Japan for the purpose of spraying fireproofing material on steel. The nineties saw rise of on-site mobile robots in routine construction, which are now considered as the most conventional and critical robots for any construction activity. Today, artificial intelligence (AI) provides new tools for

The need for such technology in the industry can be realized in the definition of an automated construction robot itself. Ever since machines came under computer control we have had automation. Though robotics provides altogether new dimensions to the technology, automated machines are, in fact, robots. They not only carry out a complex sequence of operations, but can also control their performance. They may vary from a simple tool to fully automated device, from a material handling robot that merely helps a worker install dry wall by balancing the weight of the panel to a tile inspection robot that, once started, navigates itself up a wall, taking sound data and graphically displaying results in real time. Construction work is labor intensive and is conducted in dangerous situations, also the work content and materials change frequently. Robots are thus used widely to help human workers in construction sites. A competitive, market oriented and rationalized construction tomorrow

requires developing of automated and robotized construction system today. This includes industrialized process orientation in mining, construction material production, prefabrication of construction components, on site construction, facility management, rehabilitation and recycling. The problems facing today's construction projects can be approached by flexible automation, using robots based on computer assisted planning, engineering and construction management. Influencing construction through a wide spectrum of applications The project success from the project management's viewpoint is achieved when the project is completed, bringing each of the project performance indicators (PPI)- such as cost, schedule, quality, safety, labor productivity, materials consumption or waste, etc. to an optimum value. Applying automation and robotics in construction is addressed from the perspective of raising building projects performance to serve the client and the environment. Today, there are several examples of robotics systems influencing the civil infrastructure enormously, leading to astounding performance overall. Concrete Works Applications for automation in

Teleoperated Concrete Distribution

www.masterbuilder.co.in · The Masterbuilder - March 2012

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Modular mobile light weight concrete finishing robot

Concrete Floor finishing Robot

concrete works cover material production, concrete mixing, laying, post-laying leveling, removal of surface water, and final floor finishing. Control systems for ready mix, precast, pre-stressed and block plants as well as dispatch systems for ready mix are now common at a construction site. Mixer moisture control, color batching software for solid or liquid dispensers, etc. are some examples of the same. Catching the trend, some contractors have started to use robots in concrete floor finishing. Working with soft concrete can be both physically demanding and frustrating. An intelligent horizontal distributor robot has been developed to pour concrete while it moves and levels the soft concrete. The robot can move in any direction and also avoids obstacles in the work zone, such as poles. Reducing the difficulty of concrete floor finishing by using robots like this to automate the work provides concrete contractors with a much more efficient process, allowing more time for more projects, thus generating more revenue. Remote controlled demolition robots have also been designed for dismantling concrete slabs, walls and other interior structures. In addition, efforts are underway to design a robot for concrete surface processing which receives the floor plan as an input, and after some calculations of its movement, presents it to the operator for improvement before acting. 42

Such applications, when implemented on common scale, around the globe, will probably change the overall system for concrete work. Construction of Roads Road construction projects are very expensive and highly influenced by unpredictable factors like weather, type of soil, environmental issues, etc. This has led to difficulties in developing accurate construction plans and modeling the construction operation

Sensor Based Compactor


using a traditional simulation system. The process of automated road construction starts with input data measurements carried out on the site. In road projects, the key input data includes variations in terrain, elevation and soil features. Over the past few years, laser scanning from an aircraft, helicopter or on the ground has developed greatly and become increasingly popular. A laser-scanned cloud of 3-D points adjusted to the relevant coordinate system can be imported

Larsen & Toubro Ltd


A 3-D machine control model for excavator

3-D control (Trimble, two GPS antennas) for grader

into a semi-automatic analysis application that can be used to model not only the contours of the terrain but also the tree stands, road alignments and buildings. The projects executed in the last few decades were mainly focused on the development of new generation of semi-autonomous road pavers and asphalt compactors. Road paving robots show high level of automation through automated reception of asphalt, automatic control of asphalt conveyance, asphalt spreading, steering control with mechanical sensor, paving speed and automatically controlled start/stop of all paving functions.

The use of different 3-D methods in measuring, design, machine control and as-built measuring has increased a lot. For example, laser scanning,3-D ground penetrating radar, 3-D modeling and design software's, 3-D machine control systems, the development of an integrated total process model for comprehensive automation, etc. have witnessed a considerable rise in their application. Prefabrication and modular construction The sector that represents factory built housing includes products built in factories. Thus the principles of mass

brick assembly robot

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production and customization that are the norm in manufacturing, apply to it. It is thus easy to adapt to automation, integration and optimization. In this scenario, newer materials can be applied, tight tolerances achieved, while the built products are not affected by outside climatic conditions, as is the case for site built housing. The automation pertaining to the prefab construction sector, typically falls into one of three categories:1) prefab components making process, (parts, panels, precast, formwork, etc.) which deal primarily with the construction of the building blocks; 2) assembly

Attaching the ceramic tile with hybrid construction robot system


bars or mats distributing concrete for various products such as floor, roof, wall, beam and column elements. Earthmoving

Automated Excavator

process in which the construction components are installed to create buildings, houses, etc. by an array of subcontractors, sometimes having conflicting workflows; 3) construction business processes that represent both the business and support processes like project management, supply chain management, document management, workflow management, change management, planning & scheduling, etc. In prefabricated masonry, stationary brickwork machines drastically raise

The user-interface of the 3-D control system of excavator

production capacities. Moreover, they lead to considerable relief in labor and manpower savings. A new development surge had been under way for some years, which in, individual cases has already led to Computer-Aided Manufacturing (CAM) and in some approaches to Computer-Integrated Manufacturing (CIM) of pre-fabricated concrete parts. We today are thus in the phase of promoting flexible production system using robotic cells which could execute various tasks such as setting molds, placing reinforcement

Industries such as mining and construction in which earthmoving plays a fundamental role are constantly under pressure to improve productivity, efficiency, and safety. Also, automation of field worthy earthmovers is a difficult problem. These machines must operate in unstructured, dynamic, outdoor environments, often in poor visibility conditions and rough weather. However, after decades of increments in size and power, practical limits have been reached and now automation is being sought for further improvements. Computing technology has also reached the stage where fast, compact and rugged components can match the bandwidth of sensory data. Beyond the industrial arena, which is motivated mainly by economic considerations, automated earthmoving machines are needed in worksites that are hazardous for humans. For example, NASA is interested in setting up Lunar and Martian habitats for humans, and it is expected that automated excavators will do much of the work before humans arrive. Another example is in the remediation of waste sites where chemical and nuclear wastes are stored. The cycle of operation for a fully autonomous machine is: sense, plan,

Autonomous wheel loader


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Position Emitter

Radio Emitter GPS Position Voice & Images Communication Antenna

Color Microcamara Posicion Sender Wire Handheld GPS Microphone Headphones

Microcamara Batteries

Antenna

Differential Correccion Wire

To / From Control Center

Completely equipped helmet for better safety and operation

and execute. First, an automated machine must sense its own state and the world around it. Next it must use this information along with a description of a goal to be achieved to plan the next action to be taken. Finally, the action must be executed via the mechanism. Apart from these applications, automation and robotics have extensive application in timber and steel production. It is widely used for on site and off site welding activities and to produce and erect structural steel components. Also, now it is being put to use in construction management and maintenance systems. Barriers and future of automation and robotics in construction industry

product is identical with respective tasks done over and over. However, construction robots face with different demands than conventional industrial robots. They must move about the site, because buildings are stationary and of a large size. Construction robots are also faced with changing site conditions and must be reprogrammed with each new condition. They must be able to function under adverse weather conditions including variations in humidity and temperature. Additionally, they are constantly exposed to dust and dirt on the site. Thus, there is a need to develop a robotic system for full-scale experimentation for realistic

Typically in manufacturing field, robots are stationary and product moves along the assembly line. Thus automation is easier to incorporate because each

Transportable welding robot in an integrated automated building construction site

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Carpentary aid wearable robot


assessment of automation in the construction industry. In recent years, many prototype robots have been developed, but few practical examples can be found on construction sites today. Due to the high complexity of the construction process and the stagnating technological development a longterm preparation is necessary to adapt automation to advanced construction methods. Architects, engineers and all other participants of the construction process have to be integrated in this adaptation process. The short- and long-term development of automation will take place step-by-step. It is almost inevitable that intelligent machines will find their way into construction. Without question, both the fragmentary nature and the size of this industry make it unreceptive to revolutionary changes. In addition, there are many institutional barriers. Despite these facts, there are signs that forecast a transition period in construction, and they are becoming more and more visible. Countries like USA and Japan have been the pioneers in leading the research and development of automated systems with the European Union following not far behind. India though, still has a long way to go to contribute to this rapidly evolving technology. Although the fully automated construction site is still a dream of some civil engineers, research developments have shown the promise of robotics and automation in construction.

Wirtgen India Pvt.Ltd

Ground Engineering Structural Failure

Non-compliant Building in New Zealand Meets a Fatal End Bhavani Balakrishna

C

anterbury Television (CTV) building in Christchurch, New Zealand, collapsed in the aftershock of a magnitude 6.3 earthquake causing death of 115 people and leaving several others severely injured. Built in 1986, the CTV building survived the effects of September 4, 2010 earthquake and December 26, 2010 aftershock without significant damage. However, it could not withstand the aftershock of Feb 22, 2011 since the demands greatly exceeded those anticipated in the

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structural design of the building. Not only was the building subject to considerable horizontal movement, but also amongst the highest recorded (in any urban environment) vertical acceleration. New Zealand's Department of Building and Housing recently released a report analyzing the causes of the collapse of the CTV building and three other buildings in the neighborhood. To deduce the most likely collapse scenario, structural analyses were undertaken to develop an understan-


ding of the building's likely response to earthquake ground motions, and the demands placed on the key components in the building's structure. These analyses were considered, along within formation from eye-witness accounts, photographs, physical examinations and selective sampling and testing of building remnants. As per the report, three factors played a vital role in the collapse of the building. These were the intensity of the horizontal ground shaking, lack of ductility in the columns and asymmetri-


foundations were not a factor in the collapse. The building had failed to comply with three aspects of design and construction that was expected by the standards in the year 1986 when it was built - column ductility, asymmetrical layout of shear walls and column shear strength. Also, the tests on 26 columns (21% of all CTV Building columns) after the collapse found that the concrete in many columns was significantly weaker than expected. Based on the analysis corroborated with the arrangement of the collapse debris and eye-witness reports, it is conjectured that there was an initial tilt of the building to the east initiated by failure of one or more columns on the mid to upper levels on the east face. Inter-storey displacements along this line were higher than most other locations and there was the prospect of premature failure due to contact with the spandrel panels. Loss of one of these columns on the east face would have caused the gravity load to shift to the adjacent interior columns. Because these columns were already carrying high vertical loads and were subjected to lateral displacements, collapse would have been likely. The low amount of confinement steel in the columns and the relatively large proportion of cover concrete gave the columns little capacity to sustain loads and displacements once strains in the cover concrete reached their limit. As a

result, collapse was sudden and progressed rapidly to other columns. The slabs dropped and pulled away from the north core and the perimeter beams, then the building collapsed onto its footprint pulling over the south wall onto the floor slabs. Based on the analysis of the failure of the CTV Building, the investigation panel organized by the New Zealand Department of Building & Housing concluded the following. -

-

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Geometrically irregular structures may not perform as well as structural analyses indicate. Limitations on eccentricity should be reviewed, limits tightened and the concerns brought to the attention of structural engineers and territorial authorities. The minimum confinement requirements for gravity-load bearing columns in 'secondary' structural systems must be reviewed. Adequate attachment of floors to shear walls must be achieved. There is a need to assess minimum clearance requirements to nonstructural components (for example spandrel panels and infill walls) that may detrimentally affect structural performance. Greater awareness of the importance of these requirements is needed amongst structural designers, architects, territorial authorities and builders.

Picture Source: civildefence.govt.nz

cal shear wall layout. It was also accepted that the following factors added to or may have added to the effects of the critical factors - low concrete strengths, vertical ground accelerations, interaction of columns and spandrels, separation of floor slabs from the north core and structural influence of masonry walls. The report also ascertained that the limited robustness and integrity of the tying together of building components was not a cause of the collapse but was inadequate to hold the building together when the collapse started. Also, the

Before Shock

After Shock


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Rescue workers search for signs of life in the rubble of the CTV building

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There is a need for improved confidence in design and construction quality. Measures need to be implemented which achieve this. Design Features Reports should be introduced and made mandatory. Designers must have an appropriate level of involvement in construction monitoring. There should be a focus on concrete mix designs, in-situ concrete test strengths, construction joint preparation and seismic gap achievement. There is a need to check the strength/quality of concrete achieved in arrange of structures throughout the country.

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out New Zealand. The outputs of this research would include. The Expert Panel was concerned at the level of information onsite soil conditions used as a basis for decisions on foundations. The Department is leading work with the New Zealand Geotechnical Society and their members to review geotechnical information standards. In addition the Department will develop appropriate geotechnical information standards for commer-

cial buildings, work with the sector to establish mechanisms to share geotechnical information utilizing software like BIM (Building Information Modelling) and BEIM (Built Environment Information Modelling) systems in future building design and consenting processes. The outcome sought is the appropriate level of geotechnical information to inform the design of resilient new or retrofitted buildings consistent with the seismic risk and ground conditions for the area. This will result in the right building being constructed for the conditions. In conjunction with, the Department in collaboration with the Ministry of Civil Defence and Emergency Management and the New Zealand Society of Earthquake Engineers, will lead there view of methods for post-earthquake inspection of buildings. Apart from raising awareness among building owners about post-earthquake evaluations, it also aims to reassess approaches to and general requirements for achieving earthquake resistance in buildings with emphasis on improving structural integrity and resilience, limiting the irregularity of structures,

New Zealand's Department of Building & Housing has been quick to chart out other post-investigation actionables in order to avoid repetition of such disasters. These include the following. -

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A multi-agency, multi-disciplinary research programme to use the experience in the Canterbury earthquakes to improve the understanding of building performance in earthquakes. This research will lead to potential changes to the Building Act and the Building Code and in turn to the education and training of those involved in design, construction and consenting through-

A rescue worker uses a thermal imaging camera to search for signs of life


Schwing Stetter (India) Pvt. Ltd


comes will be more effectively designed or retrofitted buildings which will perform effectively in seismic events. -

Workers and police converge on the rubble of the CTV building to seek victims

encouraging capacity design, encouraging displacement-based approaches to design and assessment, avoiding unintended interactions between structural and other parts of a building, identifying and removing critical vulnerabilities, introducing compulsory Design Features Reports for significant buildings new or retrofit and introducing tighter controls to trigger requirements for earthquake strengthening when buildings are altered or their use changed. -

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The Department has already identified and commenced the process to make the necessary legislative changes to support a more robust approach to the consenting of commercial buildings after realizing that building consent authorities do not have the right skill sets to perform their assurance function on commercial building consent applications. The Department will investigate establishing Centres of Expertise for commercial consenting as part of its work on improving the overall consenting regulatory system. The change will also include a requirement for an upfront risk profile prior to consenting and an agreed quality assurance plan for how those risks will be managed

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during construction(with the plan being audited by the consenting authority). The Department will lead a comprehensive programme of work with the Structural Engineering Society of New Zealand, the New Zealand Society of Earthquake Engineers and universities, together with the building and construction sector, to ensure the provision of revised standards and guidance on: Ÿ Ÿ

Ÿ Ÿ

Ÿ


Retrofit approaches to buildings with lightly reinforced shear walls Axial load limits for walls and columns including ductility (resilience) and confinement requirements Design of cantilever structures Suitable analysis and design methodologies for diaphragm connections and diaphragm systems with respect to construction and materials and dealing with torsional or irregular behaviour. This will be followed by input to curricula and Continuing Professional Development for practitioners in the sector and promulgation of advice to owners, territorial authorities, New Zealand Property Council and building owner organizations. The out-

The Department has already agreed to work with Cement and Concrete Association of New Zealand and leading building contractors to review the level of in situ concrete strengths. The Department will then consider actions necessary to revise standards and procedures for the manufacture, delivery, placement and curing of concrete in new buildings. The Department will oversee the implementation of the agreed changes by the relevant industry groups. The Department will also advise building owners, territorial authorities and the New Zealand Property Council of any potential issue on concrete strength. Building owners will need to assure themselves of concrete strength when they plan to alter or reassess the use of buildings, which may well become a factor in determining earthquakeprone buildings. Buildings with inappropriate concrete strength will be progressively removed from the stock as they are either upgraded or demolished.

Investigations are still on with the collapse of CTV building and it is not clear whom to hold responsible for the disaster the architects & the designers, the builders or even the Building & Housing board for outdated building codes or providing approvals and not reviewing buildings that are noncompliant with the codes. While the actionables proposed and acted on by the New Zealand Building & Housing Department are a step in the right direction, a more looming topic is the ethical question raised by this catastrophe who can be blamed for this gross negligence in the practice of engineering? Publisher's Note Picture Source www.reuters.com, www.ap.org


Urban Engineering Computational Tools

http://workshopsfactory.wordpress.com

Computational Tools Applied to Urban Engineering Armando Carlos de Pina Filho, Fernando Rodrigues Lima, Renato Dias Calado do Amaral Federal University of Rio de Janeiro (UFRJ), Brazil

T

he objective of this chapter is to present some of the main computational tools applied to urban engineering, used in diverse tasks, such as: conception, simulation, analysis, monitoring and management of data. In relation to the architectural and structural project, computational tools of CAD/CAE are frequently used. One of the most known and first software created to Personal Computers (PCs), with this purpose, was the AutoCAD by Autodesk. At first, the program offered 2D tools for design assisted by computer, presenting technical and normalisation resources. After that, the program started to offer 3D tools, becoming possible the conception and design of more detailed environments. The program is currently used for construction of virtual environments (or virtual scale models), being used together with other programs for simulation of movement and action inside of these environments.

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The Masterbuilder - March 2012 • www.masterbuilder.co.in

Another software very used currently is the ArcGIS, created to perform the geoprocessing, in which tools and processes are used to generate derived datasets. Geographic information systems (GIS) include a great set of tools to process geographic information. This collection of tools is used to operate information, such as: datasets, attribute fields, and cartographic elements for printed maps. Geoprocessing is used in all phases of a GIS for data automation, compilation, and management, analysis and modelling of advanced cartography. In addition to the programs of CAD and GIS, other interesting technology is related to Building Information Modelling (BIM), which represents the process of generating and managing building data during its life cycle using three-dimensional, real-time, dynamic building modelling software to decrease wasted time and resources in building design and construction. Some of the main software used for BIM


are Autodesk Revit Architecture and Vico Constructor. Computational tools for monitoring and management are very important for the urban development. Several urban systems, such as: transports, water and sewerage system, telecommunications and electric system, make use of these tools, controlling the processes related to each activity, as well as urban problems, as the pollution.

Other prominence developers were: Lockheed, with CADAM system, and McDonnell-Douglas, with CADD system.

Therefore, in this paper we will present details about these technologies, its programs and applications, which will t serve as introduction to the use such computational tools for study and solution of urban problems. 2. CAD (Computer-Aided Design) It is a technology largely used in the conception of projects of Engineering and Architecture. It consists of a software directed to the technical drawing, with several computational tools. Amongst the areas in which the CAD is applied, we have the Urban Engineering. Urban Engineering studies the problems of urban environments, emphasising the creation of planned environments to be sustainable, considering the balance of economic, territorial, and social factors. The infrastructure urban systems are subject of study, searching to optimise the planning of the environment, sanitation sectors, transports, urbanism, etc. It is in this context, that we can begin to understand the use of CAD programs in assisting urban projects. In respect of development of CAD software, we observe that without the postulates of the Euclidean Mathematics (350 B.C.) it would not be possible to create this computational tool. Thousand of years later, more specifically at the beginning of the 60th decade of the 20th century, Ivan Sutherland developed, as thesis of PhD in the Massachusetts Institute of Technology (MIT), an innovative system of graphical edition called "Sketchpad". In this system, the interaction of the user with the computer was perform by "Light pen", a kind of pen that was used directly in the screen to carry through the drawing, together with a box of command buttons. It was possible to create and to edit 2D objects. Such system was a landmark in computer science and graphical modelling, considered the first CAD software. In the beginning, the use of CAD software was restricted to companies of the aerospace sector and automobile assembly plants, as General Motors, due to the high cost of the computers demanded for the systems. Such software were not freely commercialised in the market. The Laboratory of Mathematics of MIT, currently called Department of Computer Science, was responsible for the main research and development of CAD software. In other places, as Europe, this type of activity was started.

Fig. 1. Example of virtual scale model: Hospital Metropolitano Norte, Pernambuco, Brazil (http://acertodecontas.blog.br)

From the 70th decade, CAD software had passed to be freely commercialised. The first 3D CAD software, CATIA Computer Aided Three Dimensional Interactive Application, was developed in 1977 by French company Avions Marcel Dassault, that bought the Lockheed, revolutionising the market. The investments, as well as the profits, vertiginously grown. In the end of the decade, programs for solid modelling already existed, as, for example, the SynthaVision of the Mathematics Application Group, Inc. (MAGI). From 1980, with the development of the first Personal Computer (PC), by IBM, the Autodesk released, in November 1982, the first program of CAD for PCs, the "AutoCAD Release 1". In 1985, the Avions Marcel Dassault released the second version of CATIA. In this same decade, the workstations (microcomputers of great efficiency and high cost, destined to technical applications) were developed, using the operational system UNIX. In the 90th

Fig. 2. Interface of AutoCAD software

www.masterbuilder.co.in • The Masterbuilder - March 2012

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decade, specifically in 1995, the SolidWorks company released the SolidWorks 95 3D CAD, revolutionising the market for used the operational system Windows NT, while the majority of the programs developed was destined to UNIX. In consequence of this, SolidWorks 95 demonstrated to be a software with good relation of costbenefit, when compared with the competitors, excessively expensive. In the following years to present time, the technology comes being improved and the software became very accessible around the world, with open access versions (freeware). An important application of the 3D CAD programs is the creation of virtual environment, also known as electronic or virtual scale models (Fig. 1). Such application is largely used in architecture projects. 2.1 Working with CAD As previously said, we had a great development of CAD software in the last decades. Amongst the main programs of CAD, the AutoCAD (http://www.autodesk.com.br) is distinguished. The software developed by Autodesk had its first version released in 1982, and recently, the Autodesk released the AutoCAD 2010.

commands substitute the necessity of navigation with the mouse to manipulate the toolbars.

Fig. 4. Example of project of Civil Engineering - a highway (http:// usa.autodesk.com)

The program generates diverse types of archive, which can be exported to other programs. Some examples: DWG (*.dwg); 3D DWF (*.dwf); Metafile (*wmf); Encapsulated (*.eps); and Bitmap (*.bmp). DWG archive is an extension shared for several CAD programs. AutoCAD is capable to import archives of the type 3D Studio (*.3ds), from Autodesk 3D Studio Max. User of AutoCAD is able to associate with your projects, programs made by programming languages, such as: Visual Basic for Applications (VBA), Visual LISP e ObjectARX. Another CAD software largely known is the SolidWorks (http:// www.solidworks.com). Developed by SolidWorks company, from group Dassault Systèmes, is a 3D CAD program for solid modelling, generally used in the project of mechanical sets (Fig. 3). SolidWorks can also be used as CAE software (ComputerAided Engineering), with simulation programs, such as: SolidWorks Simulation, and SolidWorks Flow Simulation. SolidWorks Simulation is an important tool of analysis of tensions in projects. The program uses finite element methods (FEM), using virtual application of forces on the part.

Fig. 3. Project in SolidWorks (http://www.danshope.com)

The AutoCAD (Fig. 2) is a 2D and 3D modelling program with several applications, such as: mechanical, civil, electric, and urban engineering projects; architecture; industrial manufacture; and HVAC (heating, ventilation and air conditioning). It is important to notice that the AutoCAD is also largely used as tool in academic disciplines of technical drawing. AutoCAD have commands inserted by keyboard, making possible a practical creation of entities (elements of the drawing), at the moment of the conception of the desired model, optimising the work of the designer. Such

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SolidWorks Flow Simulation is a program of analysis of draining, based on the numerical method of the finite volumes. This program allows the professional to get reasonable performance in analysis of the project under real conditions. SolidWorks is compatible with DWG files generated by AutoCAD, being able to modify 2D data or to convert into 3D data. Other interesting CAD programs include: CATIA (Computer-Aided Three-dimensional Interactive Application), developed by Dassault Systèmes and commercialised by IBM (http://www.3ds.com), and Pro/

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ENGINEER, developed by Parametric Technology Corporation (http://www.ptc.com). 2.2 Application of CAD CAD software have as main use the aid in projects of Civil Engineering and Architecture for urban environment, such as: buildings, roads, bridges, etc (Fig. 4). CAD also is widely used in the project of transmission lines of electric energy. Such practice consists in optimise the allocation

directed to employ computerized solving techniques. Precision and increasing speed for calculating multivariable operations are a good reason to use computational resources, but the quite unlimited possibilities to organize, simulate and compare data turned computer sciences on a strong allied for research and design activities. The final claim to say that now we are living in an information systems age is the large accessibility of hardware and software, the diffusion of personal systems and all related facilities: servers, networks, telecommunications, etc. An information system can be defined as an organised quiver of tools and data that can be used to answer on a systematic way questions structured by specialists. As these questions can be classified in patterns, it should be possible to build on artificial intelligence to make the system learn and deliberate by itself. If the answer to a problem employs variables associated to geographic information, it's recommended the use a dataset structure to implement and model graphic objects that represents all on earth, natural or artificial. A Geographic Information System (GIS) is a set of tools that work with data presenting three basic concepts (Fig. 5): Geodatabase, Geovisualization and Geoprocessing (Harlow, 2005).

Fig. 5. Schema extracted from ArcGIS Reference manual showing the three views of GIS

of transmission towers and wires, in accordance with the technical norms. An important characteristic is the topography of the land. Other applications in Urban Engineering include: the maintenance and update of sanitary networks, and the environmental recovery in urban areas. In the first case, CAD is used to update the database of the sewer network of the city, supplying detailed information. In the second case, CAD is used for mapping of a region, with the aid of a GPS system (Global Positioning System), identifying environmental delimitation (sources of rivers, roads, buildings, etc)(Mondardo et al., 2009).

Geodatabase represents the set of spatial data that can be expressed by rasters, vector features, networks, etc., and every rule to control their creation and management. Geovisualization is an action performed on spatial data by intelligent maps and views, from which we can view the database for querying, analysing and editing. Geoprocessing is the term used to designate operations on datasets that obtain outputs of analyses and generate new information.

There are several other applications of CAD in urban systems and areas related to Urban Engineering, and it is important to note, in practical terms, that CAD is nearly always associate to other technology: GIS (Geographic Information System), that it will be seen to follow. 3. GIS (Geographic Information System) Engineering problems were on the last 40 years gradually

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Fig. 6. Vector features overlays raster satellite image


Some engineering projects have territorial themes as industrial projects, social benefits, general infrastructure, logistics, demography, and other geo/urban/ environmental aspects. On those cases the solution involves studying geographic elements and their available information, in order to perform technical analyses. So an information system for geographic data organisation, visualisation and processing will be appropriate to those problem solving. To be efficient as a GIS, the system must perform some general tasks: acquire, convert, organise and project the geographic elements; import, organise and extract imagery, numeric and textual information; process geographic elements and information with data integrity and operational efficiency; display appropriately the data and related operations (geoprocess techniques); perform simulations and comparison of alternatives; present support for program language and custom computational routines; generate new data based on selected results; publish maps and all sort of documents for project discussion; and permit data interchange with other systems. As we can observe, GIS is designed to manage spatial data, and the geographic representation of this data can use many types of elements for plotting the information (Fig. 6): vector based features classes, as points, lines and polygons; raster datasets, as digital elevation models and imagery; networks, as roadways, pipelines, hydrology and other interlaced elements; survey measurements, as topographic annotation; and other kind of information, as postal codes, address, geographic place names, etc. These elements can be organised by layers, and could be selected by pointing or grouping for edition tasks or custom display. The selection methods could also be performed from spatial analyses or statistic classification. Georeferenced co-ordinates and related data tables of GIS elements help to improve these tasks. Geographic data representation has integrity rules (Harlow, 2005), performed by spatial relationship patterns between elements, as topologies and networks. Topologies are used to manage boundaries behaviour, to apply data integrity rules, to define adjacency and connectivity properties, to structure creation and edition of new geometry, and to express other topological operations. They are used to represent area contours, parcels, administrative boundaries, etc. Networks are used to represent graphs and their connections, controlling paths, barriers and flows. They are used to represent behaviour of pipeline, transportation, traffic, etc. Although organisation and management of spatial data can be well attempted with modern GIS programs, there is until an important aspect: how to deal with data quality.

Fig. 7. Example of a workflow model for GIS based research on industrial location

The cartographic databases can be generated from old charts or maps digitalisation, or from satellite and aerial imagery treatment. The numeric and textual databases must be converted into tables, and quite often comes from census and researches output. A great variability of data procedures can be observed world-wide when integrating data obtained from different fonts, places and scales. The periodicity of data actualisation is another deal to GIS users. The problems don't result ever from confidence, trusted fonts may have different methodological approaches, and personal interpretation can also give different valid outputs. Professional development of GIS operators can help them to detect, evaluate and work that variability, and a methodological approach is needed to treat it suitable to each research task. 3.1 Working with GIS Many users can be satisfied on using GIS as a dataset management tool for generating maps and classify data, but nowadays GIS is turning on a knowledge approach, where models incorporate advanced behaviour and integrity rules. The ultimate development on GIS procedures is directed to intelligent use of geoprocessing for built, explore and share the possibilities of geographic information. Users now are able to structure schemas and workflow models in order to improve their geoprocessing tasks, as import, check, integrate and compose data (Fig. 7). As GIS is the best way to work data from local to global level, an efficient DBMS (Data Base Management System) is needed to perform data integration, actualisation, access and sharing. As result, GIS catalogue portals based on Web nodes are increasing in number and their interoperability is part of a concept called SDI (Spatial Data Infrastructure). Servers are used to host enterprise GIS and their databases, and to provide multi-user access. Geographic Databases are employed to control and develop published data, as maps, features and tables. They are known as Geodatabase, have a proper logic to


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work with datasets by applications and tools, and perform access and management tasks. But GIS capabilities can also provide single users to customise their data. A Personal Geodatabase (PGDB) is an example of option to collect and organise features and tables attempting to user needs, using desktop computers at low cost and with feasible results. If you are a adviser or researcher and are in charge of studying urban problems, you can go ahead on mounting your PGDB, however some steps must be observed.

In other words: if you get a basic data of shapes with related table presenting geocode column you can aggregate new data from other ordinary tables that has also this geocode column. GIS also enables visualisation of each element by selecting it from geocode, and permits editing the tables to insert new columns containing yours own information. Second, you must organise your features

The start point is to structure correctly your problem, identifying the factors and conditions that impacts on, a methodological approach to face it, and a technical procedure to get alternatives and produce results. First, you must study what kind of information you need, identify the sources and think about layer and features organisation. Next, you must acquire geographic data from GIS portals or institutional sources. Many research and administrative institutions provide download of vector and raster data from their DBMS, or send it by request. If there is no available geographic data, it will be necessary to digitalis existing map and imagery, but for this task is recommended a professional with advanced knowledge of geodesics, cartography and geoprocessing. After getting the appropriate geographic information is important to know that vector data is usually related to a table, which has a column whose contents link the graphic representation to a register. Raster image has pixel position attached to a co-ordinate value. Vector features as point, line or polygon has as code number for the system link requirements, but can also have a code for geographic cadastral purposes (Fig. 8). Geocode is a tendency on GIS procedures and has the advantage to make easy later joins and relates of table data with none geographic plot.

Fig. 8. Vector features as point, line and polygon with associated table containing geocode

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Fig. 9. Use of GIS in the mapping of water and sewer ducts (http://www.gis.com)

and tables in a dataset, defining co-ordinate systems and importing independent features and tables to the PGDB. This modality of data organisation provides more security and flexibility, increasing edition and analysis tasks. Working with stand alone features can face restrictions that are not present on a PGDB structure, as it works more properly with layers, overlays, projections and coordinates. Third, you must know what to do to improve your queries on GIS ambience. It is a lost of potential to use a GIS only for data visualisation or map creation, there is more than this. Both DBMS or PGDB can generate data performing spatial analysis or statistic classification. As you have the demands of your research well structured, GIS can help you to answer by crossing multi-layer information, selecting and editing data from SQL (Structured Query Language) statements and processing new features containing partial and conclusive results. Finally, you must obtain a valid output for your problem solving, and communicate it to others on a suitable way. GIS can help you on producing thematic maps, analytical graphs and technical reports. You can also get community, representatives and specialists to work in a participative mode using GIS to generate and validate output of decision sessions. Some people have difficulties to identify and interpret geographic elements, and GIS can highlight and detach text and visual information for making it easier.

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Application of GIS GIS technology is much used in Urban Engineering to analyse, in a detailed way, characteristics related to urban planning. In addition to CAD, GIS presents solutions for several problems, and it is applied, in a integrated way, in projects of Civil Engineering and Architecture, including the most diverse urban systems (Fig. 9), making possible the maintenance and update of service networks, as well as the environmental recovery in urban areas.

technology allows to greater efficiency in the taking of decisions during the elaboration of the project, easiness in the emission of building documents, establishment of deadlines, estimate of costs, information about the analysis of risks and management of the operational conditions of the installations.

Nowadays, the accessibility of GIS technology stimulates educators to work in a new concept, called Geographical Inclusion, which can be performed on basic education class in order to provide young students with geographic visualisation and interpretative capabilities. We are living a age of saving resources, environmental care and sustainable actions, and GIS with his solving problem design and participative net work potential is the most strong partner in managing data for this purposes. Concluding the technologies presented in this chapter, we will see to follow the BIM technology (Building Information Modelling), that it represents, in a certain way, an evolution of CAD technology, previously presented. BIM (Building Information Modelling) It is a technology that consists in the integration of all types of information related to conception and execution of a project of Civil Engineering. Such information, stored in efficient database, not say respect only to design or to modelling of plants and virtual environments, but also to management of execution time of project, geographic information, quantification of material used in all building, detailing of the constructive processes, sustainability, etc. In short, the technology makes possible that the work team has an integrated vision of the project. This allows, for example, that engineers and architects idealise and execute the project sharing the same base of information. This technology has been spread together with the practice of Urban Engineering.

Fig. 10. Interface of Autodesk Revit Architecture (http://images.autodesk.com)

Using a CAD software in an engineering project, the designer inserts detailed specifications through the headings, for example: specification of the material used in the confection of a wall, manufacturer of the material, necessary amount. In the case of BIM technology, such information is directly inserted in the drawing at the moment of the modelling. Working with BIM In BIM technology, a set of tools provided by one or more software is used for: modelling of surfaces; modelling and structural calculation; management of the building; manufacture management; environmental analysis; estimate of costs; and specification.

In a certain way, BIM is seen as an evolution of 3D CAD techniques. In fact, this technology is defined as 4D CAD, where the fourth dimension is not physical, but the set of information that go beyond the engineering concepts, used in the development of the project. The use of BIM can mean an effective optimisation of time and increase of the productivity levels. Other important characteristic is the easiness to perform modifications in the project, in any phase of execution. BIM makes possible the meeting of information, such as: the documentation of licensing for building, the established environmental conditions, and other legal aspects that are of extreme importance for execution of the project. Thus, the

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Fig. 11. Interface of Google SketchUp (http://www.crackvalley.com)


Autodesk Revit Architecture (usa.autodesk.com)(Fig. 10), is one of the main BIM software, having: tools of 2D and 3D drawing; co-ordinated database, in such way that alterations performed in the information are automatically update in all model, reducing the possibility of errors and/ or omissions; associative sections of divisions table; libraries of details, that can be created and be adapted to the patterns of the project team; parametric components, that function as an open graphical system for design concern and shape creation; inventory of materials, that allows the calculation of detailed amounts of material, updating while the project evolves, on the basis of parametric alterations; etc. Fig. 14. Model of the Airport (http://bim.arch.gatech.edu)

project; exportation of DWF files (used in CAD programs); and navigation in real time. Other popular freeware is the Google SketchUp (http:// sketchup.google.com)(Fig.11), much used in the academic area, presenting modelling by means of surfaces. Such software presents limitations compared to the programs already cited. SketchUp works efficiently with information related to the localisation, size and design, reason for which is used in the confection of models that can be exported to programs, as for example, the Autodesk NavisWorks Review. There are several other programs related to BIM technology, as for example, Vico Constructor (http:// www.vicosoftware.com), presenting diverse characteristics and resources, such as: the structural analysis of the building; the constant update of the information, correcting possible errors of execution; the estimate of costs of the enterprise; etc. Application of BIM As well as CAD and GIS technologies, BIM presents a series of applications in the area of Urban Engineering, and currently it comes substituting CAD, in a effective way, because it presents advantages in relation to the management of the projects.

Fig. 12 and 13. Assembly of the structure of the Water Cube, and aerial photo of the place (http://comunicacaoexponencial.com.br)

There are other BIM programs by Autodesk, as Autodesk Navisworks (usa.autodesk.com), that it does not present tools of environment modelling, being destined to the revision of 3D projects or visualisation of models, that is the case of the freeware NavisWorks Freedom. The main tools include: aggregation of files and 3D data; revision tools; creation of 4D table; object animation; management of interference and detention/correction of conflicts in the

A current example of BIM application is the National Centre of Swimming of Pequim, China (en.beijing2008.cn/ 46/39/WaterCube.shtml). Seat of the competitions of swimming during the Olympic Games of 2008, known as Water Cube, the place have a useful area of 90,000 m², five Olympic swimming pools and capacity for 17,000 spectators, and BIM was used in all phases of the project (Fig. 12 and 13). Other example of BIM application is the International Airport Maynard Holbrook Jackson Jr., Atlanta, United States (Fig. 14). This airport is in construction phase with


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a stipulated deadline for 2011. In this project, of great magnitude, BIM is extremely necessary in the optimisation of execution time, since the old airport of Atlanta is overloaded. The estimated cost of the enterprise is approximately US$ 1.4 billion (Ford, 2009). Conclusion This chapter looked for to present the main details on three technologies much used in Urban Engineering: CAD (Computer-Aided Design); GIS (Geographic Information System); and BIM (Building Information Modelling). As it can be seen, each one of them presents specific

characteristics and with diverse applications in urban projects, providing better results in relation to the planning, management and maintenance of the systems. In relation to presented software, it is important to note that the authors do not have any connections with the cited companies. The programs were shown only as computational tools that use the presented technologies, and there are many other commercial software and freeware that can be used in works involving CAD, GIS or BIM. Therefore, the work presented here does not represent any intention of marketing for no one of cited software and/or companies. References

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Autodesk (2006). Orange County Sanitation District - Customer Success Story. Autodesk Infrastructure Solutions

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Autodesk (2009). Langan Engineering & Environmental Services - Customer Success Story. Autodesk Infrastructure Solutions

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Ford, K. (2009). Maynard Holbrook Jackson Jr. International Terminal. Holder Construction Group LLC, Georgia Tech

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Harlow, M. (2005). ArcGIS Reference Documentation. ESRI: Environmental Systems Research Institute Inc., Redlands

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Kymmell, W. (2008). Building Information Modelling - Planning and Managing Construction Projects with 4D CAD and Simulations. The McGraw-Hill Companies, Inc

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Mondardo, D., Bellon, P. P., Santos, L. B., Meinerz, C. C. & Haoui, A. F. (2009). Proposta de Recuperação Ambiental na Área Urbana da Microbacia do Rio Ouro Monte. 2nd International Workshop - Advances in Cleaner Production, São Paulo, Brazil

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Sutherland, I. E. (2003). Sketchpad: A man-machine graphical comunication system. Technical Report 574. University of Cambridge, Computer Laboratory, p. 20

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http://acertodecontas.blog.br/ Accessed in August 13, 2009

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http://bim.arch.gatech.edu/ Accessed in December 04, 2009

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http://en.beijing2008.cn/ Accessed in December 04, 2009

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http://images.autodesk.com/ Accessed in December 01, 2009

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http://usa.autodesk.com/ Accessed in November 27, 2009

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http://www.3ds.com/products/catia/ Accessed in August 24, 2009

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http://www.autodesk.com.br/ Accessed in August 21, 2009

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http://www.crackvalley.com/ Accessed December 03, 2009

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http://www.danshope.com/ Accessed in August 22, 2009

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http://www.gis.com/ Accessed in August 14, 2009

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http://www.ptc.com/products/proengineer/ Accessed in August 24, 2009

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http://www.solidworks.com/ Accessed in August 22, 2009

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http://www.vicosoftware.com/ Accessed in December 03, 2009


Urban Engineering Traffic Management

Picture Source: www.mobility.siemens.com

Intelligent Traffic Management Systems: A Growing Necessity Bhavani Balakrishna

A

s per a World Bank report, the density of India's highway network (0.66) is on par to that of the United States (0.65) and several times greater than that of China (0.16) or Brazil (0.20). In metropolitan and major Indian cities like Mumbai, Delhi, Ahmedabad, Bangalore, Chennai and Hyderabad, traffic is growing four times faster than the population. With increased urbanization and increase in vehicular traffic, cities everywhere are battling an increase in demand and an inability to build sufficient infrastructure

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to cope. While the Government has been laying emphasis on building roads, bridges and underpasses and creating alternative modes of mass public transport systems, this may not be sufficient to address the traffic congestion. Traffic management has always posed a challenge in India and it may continue to become more difficult with every passing day unless we start building some intelligence into the way we look at resolving these issues. The solution lies in leveraging advanced technologies and intelligent


solutions. Some intelligent traffic management systems are already being implemented in cities like Delhi and Bangalore making an impact in the form of reduced congestion less fatal accidents. Other cities are likely to follow suit soon. Subset of a larger subject, Intelligent Transportation System (ITS), intelligent traffic management systems assist road authorities in maximizing the operational performance and reliability of all aspect of the road network. Intelligent Transport Systems (ITS) is essentially the


application of computer and communications technologies coming in aid of the transport problems. This may involve use of CCTVs in strategic junctions, vehicle presence detectors, in-road magnetic loop detectors and other remote video surveillance devices to assure automated control in good or bad weather and in varying traffic volumes. Based on real-time data and historical data, the traffic management system alters traffic signal cycles in real time, based on the in-situ sensors or surveillance devices, to respond to changing traffic conditions. These traffic control systems feed data from individual controllers at each intersection to master controllers that can synchronize a group of the individual controllers. The main control center receives information from all master controllers, allowing operators to monitor the entire system continuously, issue control commands when necessary, and optimize deployment of field personnel as needed for operations and traffic security. Centralized information collection supports statistical analysis and historical files for subsequent strategic evaluation. A remote control center backs up the main control center for optimum security. There is already some amount of research and resources being dedicated to this area. The Center of Excellence in Urban Transport (COEUT) set up in IIT-

Underground electrical wire

System Computer

electromagnetic field

Induction-loop Traffic Sensors Madras comprises people from various disciplines and is working closely with the ministry on research in ITS. The center works with various private firms who are developing innovative solutions for better transport. However, their prime challenge is the lack of systematic data collection. Collection of real-time traffic information on highway segments and surface street networks is critical for the success of a ITS or ITMS system. As mentioned above, data could be collected from videos, vehicle detectors, probe vehicles (automatic vehicle identifiers and

electrical meter

automatic vehicle locators) or GPS. Most developed countries use inductive loop detectors (ILD) for applications like vehicle detection, incident detection, automatic traffic surveillance, real-time traffic adaptive signal control, and data for traveler, commercial and emergency information services, mainly because it can collect data without any need for public participation. However, the loop detectors designed for the developed countries are designed assuming lane discipline and homogeneous traffic which is absent in India. Also, the vast range of vehicular types (bicycle, two wheeler, three wheeler, light motor vehicle, heavy motor vehicle) that need to be identified for accurate traffic data collection is a major challenge for the existing ILD systems. The COUET at IIT-Madras has developed a new type of loop detector suitable for Indian traffic conditions. The principal components of an inductive loop detector system include one or more turns of insulated loop wire wound in a shallow slot sawed in the pavement, a lead-in cable that runs from the curbside pull box to the controller cabinet, and a detector electronics unit housed in the controller cabinet. When a vehicle passes over the loop or stops within the loop, it


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Components of an Intelligent Traffic Management System Involves a complex array of layers to define an overall system. Technology only forms part of the overall system. Two principle components form a typical system, namely the technology layer and the institutional layer. Information is collected, processed and disseminated within the traffic management system. This information could be commands to roadside traffic controllers from a central computer to change the green times based on optimal traffic flow, or it could be the dissemination of existing traffic conditions via a radio broadcast. Technology The technology components include: -

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Road side devices such as CCTV cameras, linked traffic controllers, variable message signs, used to control, monitor and manage traffic, Telecommunications networks including fibre-optic, copper lines and wireless media, used to link the road-side devices to a central operations centre, and Traffic management computers in a central operations centre, which analyze, process, record and disseminate traffic management information as well as control roadside devices.

Institutional The institutional components include: -

People to operate the systems and to provide a public interface to the system, and co-ordinate traffic management and systems related activities, Operational procedures, and standards which include maintenance processes, incident management protocols and responses, and Traffic engineering inputs to the system, including planning, analysis and design of individual traffic management components and the coordination with the overarching transport planning processes

decreases the inductance of the loop. The change in inductance helps in identifying various parameters such as vehicle speed and vehicle length, which also helps in processing the current traffic speed and the traffic count in the specific area. It can also sense vehicles of different sizes (for example, it can identify a bus from a bicycle) as they go through the roadways. The data can be used for creating a traffic data centre where all traffic data can be archived and shared among the transportation researchers across India. However, intelligent traffic management systems will be set up for failure despite the availability of technology and availability of data. Many cities have invested in a number of advanced traffic management systems which can be deemed to have failed to deliver the expected benefits due to the failure, not of the technology elements, but because

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of the failure of the institutional element. Success requires strong backup in terms of policy, legislation, regulation and relevant sector coordination and common action. Practical Applications The Delhi police has a budget allocation of ` 82 crore of for funding the Intelligent Traffic Management System. The project will approximately cover 220 kilometers of urban major roads with around 240 signal intersections. The main components include a traffic control and management centre, a disaster recovery centre, an incident detection system on expressways and adaptive signal control of at-grade intersections. It will also involve a CCTV camera system, traffic information system with variable message signs, adaptive speed control on national highways, speed and red light violation cameras and a parking management


system. However, despite the ambitious plans, previous tender requests failed to find a suitable bidder. A similar scheme has also been implemented in Bangalore, where the State government has promised to spend Rs 79 crore to help Bangalore police improve traffic management. In Bangalore, the operation is run from the dedicated Traffic Management Centre, a technology centre at the heart of Bangalore's police where a team remotely manages the city's traffic. Nearly 120 cameras at different junctions are remotely monitored. Out of 300 traffic signals in Bangalore, 163 have already been connected to the traffic management centre. Of these, 120 are vehicle activated, meaning that if there is a four second period where no vehicles pass through, the signal automatically turns to red. As part of the Mumbai City Mobility Management project, Traficon has been awarded a contract for installing nearly 700 vehicle presence detectors at Mumbai's various busy road junctions controlled by traffic signals. By detecting both waiting and approaching vehicles, these intelligent 'all-in-one' cameras will be used for optimization of traffic signal timings and to cut down waiting time at traffic lights. Based on the information coming from these surveillance devices and Telvent's in-road magnetic loop detectors in-situ sensors, Mumbai's Adaptive Traffic Control System (ATCS) by Telvent alters traffic signal cycles in real time to respond to changing traffic conditions. Once fully operational, ATCS is expected to cut down waiting time at traffic signals by almost half. For the city of Chennai, the decision to use Traficon's integrated video sensor technology was taken after a competitive bidding mid 2010. Today up to 100 TrafiCam sensors are installed and operational to detect waiting vehicles at multiple intersections across the city. KSRTC (Karnataka State Road Transport Corporation) will soon be implementing the intelligent transport system (ITS) for Mysore city under GEF (Global Environment Fund) SUTP (Sus-



tainable Urban Transport Programme), the initiative by World Bank. The overall scope of implementation will consist of design, development, testing, installation, commissioning, training, operations, and management of facilities, for a period of three years by the winning bidder. The project plan covers 500 buses, 80 bus stops, and 10 bus terminals. It will have several components including vehicle tracking system, central control station, passenger information management system, communication sub system, travel demand management, incident and emergency management system, operational and maintenance specification and fleet management system. Core technologies include geographical positioning system (GPS), electronic display systems, and information & communication technologies. The cost of the project is ` 19.13 crores that covers the capital costs and three years' operating costs with a project contingency of 5%. There are further projects in the pipeline across India such as implementation of ITS in Indore, Pune, etc. According to the Centre for Development of Advanced Greater Hyderabad will have a master plan for Intelligent Transport System (ITS) soon. The study

will cover the Outer Ring Road (ORR) with the main focus on the Inner Ring Road (IRR) and integration of traffic departments. The ITS is meant to support optimisation of traffic flow, reduce environmental impact on the transportation sector, reduce road accidents and promote efficiency in traffic and transportation operation and manage ment. The study of ITS master plan will be undertaken in two phases and completed in 18 months by January 2013. Again, while the above initiatives show immense promise, we need to develop standards of roads and customize traffic control devices to Indian conditions and mixed traffic conditions and need to update our legislation. Such modern practices of

traffic management and case studies of their implementation in the developed countries should figure as an important part in the curriculum of police academies and schools. Modern tools and systems of enforcement are not available to traffic police authorities except in major metropolitan cities. In all, India has started taking baby steps in implementation of intelligent traffic management systems and an integrated transport management system but the country still has a long way ahead. Publisher's Note Picture Source www.auto.howstuffworks.com www.indiatransportportal.com www.in.reuters.com

A Charming Shipping Container Home

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n industrial home namely, Maison Container Lille has been built in France by spreading out and stacking shipping containers. Patrick Partouche, the designer of the daring 3-bedroom home, used 8 shipping containers that were assembled to erect the structure in just 3 days, in 2010. The windows have been cut out from the container ends, while the cargo doors can be kept open or closed to render shade or privacy, or to protect from storms. With sparkling cherry-red exterior and dazzling white interior walls, the 240 sq m building has a car garage, storage space,

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kitchen, dining space and living area organized in an open floor layout, said a report on the project on popular online blog Inhabitat. Red columns and metal finishes


highlight the interiors, while the windows are argon-filled and smeared with low e-coating for enhanced efficiency. The roof forms a shade-screen to allow air flow and prevent overheating. It is a protective cover rather than a water shedding component. In the first floor, some floor parts have been removed to provide double-height for the ground floor. Metal walkways over the area lead to the bedrooms, bathroom and office room. Parts removed from the containers have been creatively used to make furniture and to decorate the interiors, further added the report in the blog.

Igloo Tiles

Sustainable Infrastructure

The Beijing Bohai Innovation City MB Report

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kidmore, Owings & Merrill LLP (SOM), one of the leading architecture, interior design, engineering and urban-planning firms in the world, emerged as the winner of the master plan for “Beijing Bohai Rim Advanced Business Park” competition held jointly by Beijing Tongzhou District Taihu High End Headquarters Construction Management Committee and Beijing Xinghu Investment and Development Co. Ltd. The Beijing Bohai Innovation City is part of China's commitment to transitbased, environmentally sensitive planning focusing on rapid development of satellite cities along Chinese high speed rail corridors. The city also aims to serve as the primary headquarters location for advanced industries in the rapidly growing Bohai Rim, a region

that at present accounts for more than a quarter of China's GDP. The masterplan proposed by SOM reflects a new model of compact, environmentally enhanced urban design plan that concentrates walkable, compact densities around transit stations, while still preserving existing agriculture and green space. It cleverly leverages the use of the economic and lifestyle assets of the Beijing-Tianjin corridor by centering the new environmentally friendly district along the highspeed-rail line linking the national capital to the port city of Tianjin. The design involves 17.6 million square meters of mixed-use development with half the 1,473-hectare site allocated to open space and nature. The Beijing Bohai Innovation City

masterplan revolves around a central business district organized around a high speed train station and five distinct neighborhoods that offers diverse housing, education, shopping and work destinations. The plan allows the residents to use multi-modal transportation network highlighted by the city's close proximity to the existing capital airport and a potential new international airport south of Beijing. By linking high-speed rail with metro lines and providing alternative modes of public transport such as bus rapid transit, local streetcars and a state-of-the-art electric car fleet, it is expected that 80 percent of the city's personal transportation can be achieved by transit, walking and bicycling. The pedestrian and bicycle friendly street designs should also help the residents to connect to neighboring workplaces, schools and cultural amenities along green streets and corridors. SOM's winning design scheme is built upon landscape design firm Turenscape's proposed central wetland park that uses functional environmental systems to filter and clean storm water before returning it to adjoining rivers. The design also sets specific and aggressive goals for water, energy, waste, renewable energy and building design efficiency. Picture source: SOM

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URC Infotec Pvt.Ltd

Urban Engineering BIM

http://www.urbanbydesign.org

Sustainable Design Analysis and Building Information Modeling Manideep Saha Head, AEC & Geospatial, Autodesk India

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he world is changing, the economy is changing, and the architectural practice is changing. Designing energy- and resource-efficient buildings, in many locations, is no longer optional, but mandatory. While owners have always sought designs that are cost-effective to operate and that will command premium lease values, research shows that green buildings (for example, LEED®-certified) are more likely to deliver on these criteria. A 2008 report from McGraw Hill Construction finds a 13.6 percent decrease in operating costs from green building and a 10.9 percent increase in building values as reported by architects, engineering firms, contractors, and owners over the past three years. (McGraw Hill

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Construction September 19, 2008) More pressing is the growing number of local and national regulations that mandate targets for energy and resource efficiency as well as carbon emission reductions in new and renovated buildings. These government initiatives are certainly put in place to help reduce greenhouse gas emissions and slow our impact on climate change, but they are also instituted to reduce dependence on unpredictable markets for oil as an energy source and, most recently, to help stimulate the global economy. Sustainable Design in Practice Design decisions made early in the process can deliver


significant results when it comes to the efficient use of the vital resources. Employing sustainable analysis tools helps architects and engineers to make better informed decisions earlier in the design process and enables them to have a greater impact on the efficiency and performance of a building design. Historically, analysis softwares were complex and required special training-making them unsuitable for infrequent users such as architects or designers. Sustainable analysis tools, such as Autodesk Ecotect Analysis helps users to become proficiently faster by providing access to immense stores of data and the ability to more quickly iterate for optimal sustainable designs.

Figure 2: The link between the Revit platform and the Autodesk Green Building Studio web-based service is facilitated through a plug-in that enables registered users to access the service directly from their Autodesk Revit Architecture design environment.

Designing and delivering more sustainable projects can be complex. It requires close coordination across different project stages, from design through construction and operation. Many firms are looking for the best way to integrate building information modeling (BIM) technology with sustainable design and analysis tools. BIM is core to Autodesk's sustainable design approach for building performance analysis and simulation.

Performing these analyses in a CAD workflow is a fairly difficult undertaking as the CAD model has to be exported and carefully massaged to work with analysis programs. Using the Autodesk Ecotect Analysis to analyze early building designs emerging from a Revit-based BIM process can simplify the analysis process.

Analyzing a Building Design

The Autodesk® Green Building Studio® web-based service enables faster, more accurate whole-building energy, water, and carbon emission analyses and helps architects-the majority of which are not specially trained in any of these analyses-to evaluate the carbon footprint of a Revit-based building design with greater ease.

BIM enables architects and engineers to use digital design information to analyze and understand how their projects perform before they are built. Developing and evaluating multiple alternatives at the same time enables easy comparison and informs better sustainable design decisions. A computable Autodesk® Revit® Architecture design model is devised for sustainability analyses-even during early conceptual design. As soon as the layout of a building's walls, windows, roofs, floors, and interior partitions (elements that define a building's thermal zones) are established, the information employed to create a Revit® model can be used to perform analyses.

Whole Building Energy, Water and Carbon Analysis

Built specifically for architects and using green building extensible markup language for easy data exchange across the Internet, the web-based service was one of the first engineering analysis tools to deliver easy-to-use interoperability between building designs and sophisticated energy analysis software programs such as DOE-2. The link between the Revit platform and the Green Building Studio web service is facilitated through a plugin that enables registered users to access the service directly from their Revit Architecture design environment. Inline Energy Analysis The Autodesk Green Building Studio web-based service enables architects and other users to perform faster analyses of a Revit-based building design, from within their own design environment, directly over the Internet. This helps streamline the entire analysis process and enables architects to get faster feedback on their design alternatives-making green design more efficient and costeffective.

Figure 1: The Autodesk Green Building Studio web-based service enables faster, whole-building energy, water, and carbon emission analyses of a Revit-based building design. The building location (being defined here) drives the resulting electricity and water usage costs.

Based on the building's size, type, and location (which drives electricity and water usage costs), the web-based service determines the appropriate material, construction,


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system, and equipment defaults by using regional building standards and codes to make intelligent assumptions. Using simple drop-down menus, architects can quickly change any of these settings to define specific aspects of their design; a different building orientation, a lower U-value window glazing, or a 4-pipe fan coil HVAC system. The service uses precise hourly weather data, as well as historical rain data, that are accurate to within 20

Figure 4: The Autodesk Revit-based software application user views the output of the analyses in a web browser, including the estimated energy and carbon emission summaries (shown left) and a detailed LEED water efficiency guide (shown below).

kilometers of the given building site. It also uses emission data for electric power plants across the United States and includes the broad range of variables needed to assess carbon neutrality. Analysis Results Usually, within minutes the service calculates a building's carbon emissions and the user is able to view the output in a web browser, including the estimated energy and cost summaries as well as the building's carbon neutral potential. Users can then explore design alternatives by updating the settings used by the service and rerunning the analysis, or by revising the building model itself in the Revit-based application and then rerunning the analysis. Figure 3: Architects and other users can explore design alternatives by updating the settings used by the Autodesk Green Building Studio web-based service and rerunning the analysis, or revising the building model itself in the Revit-based application and then rerunning the analysis.

The output also summarizes the water usage and costs, and electricity and fuel costs; calculates an ENERGY STAR score; estimates photovoltaic and wind energy potential; calculates points toward LEED daylighting credit; and estimates natural ventilation potential. Unlike most analysis output, the Autodesk Green Building Studio report is easier to understand-giving architects and other users actionable information they need to help make greener design decisions. Detailed Environmental Performance The desktop tools in Autodesk Ecotect Analysis provide a wide range of functions and simulations, helping architects and other users to understand how environmental factors will impact building operation and performance in the early design phase. Working with the Environment To mitigate a building's impact on the environment, it is important to first understand how the environment will impact the building. Built specifically by architects and focused on the building design process, Autodesk Ecotect Analysis is an environmental analysis tool that enables

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Tekla India Pvt.Ltd


access, and visual impact. Revit-based design models can be exported to gbXML format and imported directly into Autodesk Ecotect Analysis for simulation and analysis throughout the design process. At the onset of the design process, very early stage Autodesk Revit Architecture massing models can be used in combination with site analysis functionality in Autodesk Ecotect Analysis to help determine the optimal location, shape, and orientation of a building designbased on fundamental environmental factors such as daylight, overshadowing, solar access, and visual impact.

Figure 5: Early stage Autodesk Revit Architecture models can be analyzed with Autodesk Ecotect Analysis to help determine the optimal location, shape, and orientation of a building design-based on basic environmental factors such as the overshadowing of a particular building (highlighted in red) shown here.

designers to simulate the performance of their building projects right from the earliest stages of conceptual design. Autodesk Ecotect Analysis combines a wide array of analysis functions-including shadows, shading, solar, lighting, thermal, ventilation, and acoustics-with a highly visual and interactive display that presents analytical results directly within the context of the building model. This visual feedback enables the software to communicate complex concepts and extensive datasets more effectively and helps designers quickly engage with multifaceted performance issues-at a time when the design is sufficiently "plastic" and can be easily changed.

As the conceptual design evolves, whole-building energy, water and carbon analysis can be conducted using the integrated access to Autodesk Green Building Studio in order to benchmark its energy use and recommend areas of potential savings. Once these fundamental design parameters have been established, Autodesk Ecotect Analysis can be used again to rearrange rooms and zones, to size and shape individual apertures, to design custom shading devices, or to choose specific materials-based on environmental factors such as daylight availability, glare protection, outside views, and acoustic comfort. Visual Feedback Perhaps the most unique aspect of the software is its visual and interactive display of the analysis results. The inability of the designer to easily interpret the results of analyses is often the biggest failing of building performance analysis software. Autodesk Ecotect Analysis provides actionable feedback to the designer in the form of text-based reports

Analyzing a Design in the Context of BIM Revit-based design models can be exported to gbXML format and imported directly into Autodesk Ecotect Analysis for simulation and analysis throughout the design process. At the onset of the design process, very early stage Autodesk Revit Architecture massing models can be used in combination with site analysis functionality in Autodesk Ecotect Analysis to help determine the optimal location, shape, and orientation of a building design-based on fundamental environmental factors such as daylight, overshadowing, solar

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Figure 6: Autodesk Ecotect Analysis can also be used for detailed design analysis. For example, the visibility analysis displayed here shows the amount and quality of views to the outside mapped over the floor area of an office.

Savcor India Pvt.Ltd


time. For instance, a designer can rotate a view of surface-mapped solar radiation looking for variations over each facade, or watch an animated sequence of solar rays to see how sunlight interacts with a specially designed light shelf at different times of the year. Ongoing Building Performance Analysis During conceptual design, Autodesk Ecotect Analysis and the Autodesk Revit Architecture model can be used for a variety of early analysis. For example, the designer can perform overshadowing, solar access, and wind-flow analyses to iterate on a form, and orientation that maximizes building performance without impinging on the rights-to-light of neighboring structures.

Figure 7: Using Autodesk Ecotect Analysis, architects can see the results of their analysis displayed in the context of a building model, such as the surface-mapped results of this solar radiation analysis.

as well as visual displays. These visual displays are more than just charts and graphs. The analysis results are presented directly within the context of the model display: shadow animations resulting from shadow casting analysis; surface-mapped information such as incident solar radiation; and spatial volumetric renderings such as daylight or thermal comfort distribution in a room. This type of visual feedback lets designers more easily understand and interact with analysis data, often in real

As the design progresses and the elements that define a building's thermal zones are established (the layout of the walls, windows, roofs, floors, and interior partitions), the Revit model can be used for room-based calculations such as average daylight factors, reverberation times, and portions of the floor area with direct views outside. Eventually the Revit model can be used for more detailed analysis-such as shading, lighting, and acoustic analysis. For example, the designer can use Autodesk Ecotect Analysis in conjunction with a shading louver design modeled in Autodesk Revit Architecture to simulate how the design will work under different conditions throughout the year. Or the architect can use Autodesk Ecotect Analysis to help assess the acoustic comfort of a Revitbased design, and then adjust the location of a sound source or adjust the internal wall layout or the geometry of sound reflectors for optimal comfort. Summary

Figure 8: Autodesk Ecotect Analysis software also displays analysis results using spatial volumetric renderings, such as this analysis of the visual impact of a building within an urban site.

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The consistent, computable data that comes from Autodesk Revit Architecture combined with the breadth of performance analysis and meaningful feedback of Autodesk Ecotect Analysis work in combination to help reduce the cost and time to perform energy modeling and analysis. The feedback from these analyses helps architects and other users to optimize the energy efficiency of their designs and work toward carbon neutrality earlier in the design process-a key ingredient not only for incorporating energy efficiency into standard building design practices but also for mitigating the carbon footprint of our built environment.

Neocrete Technologies Pvt. Ltd

Communication Feature

TM

URCIMS – En-Route to a Systematic Future

C. Devarajan CMD - URC Infotec Pvt Ltd.

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he construction industry in India is chronically plagued with issues such as limited visibility of remote sites, higher probability of

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budget and time overrun, inability to track men and material at both procurement and usage and above all, opaqueness of the financial performance of each project. URC Construction Pvt Ltd, established 56 years ago at Erode, was no exception to this trend. Hence, in 2002 the company searched for a cure through an IT solution; but a complete and integrated solution with a clear understanding of construction industry and its challenges was not available in the market. The IT solutions that were available at that time came with promises of full filling the requirements of URC only by customization during the time of implementation. However, the company was wary of the idea of building non-


existing core modules in the form of customization during implementation and/or bridging two or more disparate systems at the time of generating key MIS reports. Thus, URC formed a team to build an ERP system that would exclusively be a solution to the construction industry. Using advanced IT technologies, the team with convergence of experts from construction core, business operations and IT developed an ERP namely URCIMSTM that linked all departments, sites and employees at all levels. In 2008 the team was spun off to form a new company called URC Infotec Pvt. Ltd (URCI). Since then the product is rolled out to NCC (formerly known as Nagarjuna Construction Company), Hyderabad


and few other construction companies. Because the product was developed by the very same people who were involved in day-to-day operations in construction core, special focus was given to areas where it would matter a lot to any construction company. For example, the management shall decide to create or not to create budget at company and/or site level and set the level of budgetary controls in operations. Even budget shall be revised as a whole or only select few items as and when required. The flexible options of using and tracking revisions of budget have enabled the management and users to maximize the benefit of budget controls at sites. Similarly, URCIMSTM helps to collect and track the output of each machine/tool. Apart from collecting the usage data of plant, machinery and formworks, the output data shall be analysed specific to construction

activities. Hence, the utilization, expenditures and output of equipments in each activity shall be pared against the overall performance of the site. Additionally, the ability of the system to collect, link, track and analyze data at activity level has given the management to perform site wise profitability analysis online any time. Also, the ability to set the granularity of control of operations has given the management the control to take corrective actions. The data from modules not only from back operations such as inventory, procurement, HR and Finance & Accounts but also from execution, monitoring, plant & machinery, billing and optionally planning and tendering is fully integrated. Hence, the software package is readily available to meet the needs of most of the construction operations without much of customization.

CMD testimonial “ To h a r n e s s t h e g r e a t e s t opportunity in building infrastructure in our country with trillions of dollars infused by the Indian government, we in the construction industry should become systematic companies. Hence, a good product for operational management, process controlling and system orientation is the need of the TM hour. After implementing URCIMS in URC, NCC and other companies, I believe it is the system that will take your company to grow multi fold in the coming decade”

For further details: URC Infotec Private Limited Mob.: +91 9865653530 E-mail: [email protected] Web: www.urcims.com, www.urcinfotec.com


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'IT' Providing an Impetus for the Surveying Industry

Kota Krishna Kamath Managing Director, Esurveying Softech (India) Pvt Ltd

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lthough distance measurement is done from ages, Survey Engineering is not a very old science. It was started in 1511 with the invention of the compass, followed by invention of Chain in 1620. Theodolite was invented in 1720 and until 1990 its growth was slow. Progress in Survey Engineering has been considerable in last 20 years and the Scope of Surveying has also increased greatly. Let us have a quick look at Major IT Implementations which are used in Modern Surveying. However, the old instruments like Chain are still being used. Depending on scope of projects different new techniques, instruments and technologies are being used in Modern Survey Engineering Projects. Survey Engineers started using Computers like the way other people started using it in different fields. Initially CAD (AutoCAD, Micro Station) was introduced to prepare Survey Drawings. Then for back office Automation, tools like Word, Excel were used. Internet contributed majorly in speeding up the Survey work. Till EDM was invented there was no direct connection between Survey instruments and computers. Then started the era where noting down the point information became old style. Now, once the survey is done all the information is stored in the instrument

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and it is directly downloaded to a computer. Total Station is one instrument which is widely used in modern survey engineering. Total stations were available from 1990, and the technological boom has considerably increased both the accuracy and precision in Survey Engineering. Scope and application of Survey engineering has also increased considerably. Following Technologies are being used in Modern Survey Engineering Projects: Total Station: The total station is an electronic theodolite (transit) integrated with an electronic distance meter (EDM) to read slope distances from the instrument to a particular point. GPS: The Global Positioning System (GPS) is a space-based satellite navigation system that provides location and time information in all weather conditions, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites. DGPS: Differential Global Positioning System is an enhancement to Global Positioning System that provides improved location accuracy, from the 15-meter nominal GPS accuracy to about 10 cm in case of the best implementations. Remote Sensing: Remote sensing is the acquisition of information about an object or phenomenon, without making physical contact with the object. In modern usage, the term generally refers to the use of aerial sensor technologies to detect and classify objects on Earth. Photogrammetry: Photogrammetry is the practice of determining the geometric properties of objects from photographic images. LIDAR: Light Detection and Ranging is an optical remote sensing technology that can measure the distance to, or other properties of a target by illuminating the target with light, often using pulses from a laser.


“A worldwide network of observatories uses LIDAR's to measure the distance to reflectors placed on the moon, allowing the moon's position to be measured with mm precision”. You can make out how the Precision of Survey has increased with IT Implementations. When a large-scale project requires survey-grade spatial data, LIDAR has proven to be the fastest and most accurate technology for mapping and modeling. There are software's designed to do computation like Contouring, Earthwork, Interpolation, Section Generation which are specific to Survey Engineering. With advent of technology, Geo Browsers are also made available and Google Earth is the most popular among them. Using Google Earth and related software's, for small scale requirements results can be derived even without doing the actual Survey. As any other industry Survey Engineering has fully reaped benefits of IT improvements and the work that used to take lot of time otherwise are being done quickly and accurately. Scope of Survey Engineering also has grown Leaps and Bounds with the aid of IT. The toping on the Ice is that all these IT Solutions are becoming more affordable day by day. Mr.Kota Krishna Kamath, Managing Director of ESurveying Softech (India) Pvt Ltd, has more than 16 years' experience in software product development for both domestic and overseas market. He has architected many products in the areas of Office Automation, Taxation and Survey Engineering. India's highest selling Payroll product, 'Saral PayPack' and TDS Package, 'Saral TDS' were initially developed under Mr.Kamath's guidance. He is also the brain behind immensely popular survey related software like 'ESurvey CAD' and 'ESurvey Lisps'.

For further details: Esurveying Softech (India) Pvt. Ltd Ph: +91-80-23491717, E-mail: [email protected] Web: www.esurveying.net

Metal Tech Constructions Pvt.Ltd


Benefits of BIM Technology in Reinforced Concrete Industry

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uilding Information Modelling (BIM) is the process of modelling and communicating the structure of a building in detail to benefit the entire building lifecycle. Building Information Modelling facilitates the exchange and visualization of building information in digital 3D format between all project disciplines to ensure integrated project delivery (IPD). The acronym BIM is also used for the terms “Building Information Model” and “Building Information management”. This enables the highest level of constructability and production control. Centralizing model and non-model based data into the 3D model allows for more collaborative and integrated project management and delivery from conceptual design to construction. Tekla Structures BIM software provide an accurate, dynamic, and data-rich 3D environment that can be shared by contractors, structural

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engineers, steel detailers and fabricators, as well as concrete detailers and manufacturers Majority of the Reinforced Concrete projects are still done in 2D CAD & most of them ask whether 3D BIM can be adopted for Reinforced Concrete projects. The answer is yes & it is happening. In the drawing based workflow once the drawings are freezed for construction from the Clients or Consultants, the Contractor needs to prepare the detailed rebar drawings with the bar bending schedule. Even consultants issue the separate drawings for MEP, Post tensioning etc., where co-ordination between different groups like Design detailing, Cost estimation, Quantity management, Resource planning, Scheduling, Sub Contractor Coordination & Site Execution is a big challenge. In the Building Information Modelling workflow, Tekla Structures


effectively integrates into any best-ofbreed software driven collaborative workflow, which is the key to minimize errors and maximize efficiency, resulting in high profitability and on-time project completion. The working concept of Tekla structures Building Information Modelling for Reinforced Concrete is, a 3D parametric model based approach wherein the deliverables like Drawings (General arrangement, Foundation, Slab, Beam, Shear wall, Column schedules etc.,) along with Bar bending schedules, Material takeoff (Bill of Materials), Scheduling, Architectural & MEP information can be handled. This BIM model efficiently handles any changes in the related deliverables. Model based workflow has huge leverage in streamlining the whole value chain. The detailed BIM model has a huge potential to reduce errors & wastages in all stages starting from

Nawa Engineers & Consultants Pvt. Ltd


conceptual design to actual site execution. When one optimizes only a part of the process, like drawing production, benefits are limited. Whereas if we look to optimize the entire value chain that includes suppliers, vendors and subcontractors, the leverage of

accurate model data is enormous. The cost Impact of an error during any point of process will be multiplied once when (error) is accepted to the next stage of the process. The model based design & detailing workflow prevents most of these errors. The data from these BIM model

can be further maximized through the use of this information in the field. Traditional construction methods lose the accuracy of Model when implemented in the field. Valuable time and accuracy can be lost by manually scaling distances, calculating angles from plans, turning angles with Theodolites, and pulling tapes to measure distances. To connect the inherent accuracy of a fully coordinated BIM with the final building product, this detailed information available can be used by construction professionals to automate the layout, erection and construction of their projects.

For further details: Tekla India

Ph: +91-22-61387777, +91-80-65461546, E-mail: [email protected] Web: www.tekla.com

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Universal Construction Machinery & Equipment Ltd

Concrete Benefits

Concrete VS Asphalt Battle for the Future Choice of Construction Material

D

espite being one of the oldest materials on earth and the world's most consumed manmade material, scientists are only now beginning to decipher the behavior of concrete at an atomic level. The Concrete Sustainability Hub at MIT, whose work is being funded under a $10-million, five-year grant from the Portland Cement Association and Ready Mixed Concrete Research and Education Foundation, believes that understanding microstructure in concrete will yield new ways to manipulate the building material. The MIT's Concrete Sustainability Hub is already creating controversy through its recent report on life-cycle cost analysis (LCCA) titled "The Effects of Inflation and Its Volatility on the Choice of Construction Alternatives" wherein it suggests that life-cycle costs of investments in roads, buildings and other infrastructure should use escalation rates indexed to a material's historical inflation rate rather than to a fixed, general inflation rate. Economists use life-cycle cost analyses to help calculate the total lifetime costs of a project,

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including initial construction, rehabilitation, maintenance, and salvage value. Traditionally, LCCAs have ignored the possibility of future changes in relative prices of building materials by assuming that the real prices of all construction inputs remain fixed i.e. a standard inflation rate is used for all building materials. MIT researchers reviewed the data on real price changes of four basic construction materials concrete, asphalt, steel, and lumber and found that the assumption of constant real costs is seriously inconsistent with historical experience. Ignoring that experience can lead to serious cost overruns. To avoid such overruns, the study suggests the use of material-specific escalation rates. The paper forecasts real asphalt prices rising by 95%largely due to oil prices and real concrete prices dropping by 20% over the next 50 years. It sees steel and lumber prices falling a respective 28% and 44% in the same period. In other words, researchers found that the actual total life-cycle costs of using asphalt could be much higher than the


*Magnified view of concrete with nanoscale crystal seeds, Scale 960:1 (bei 12 cm in width)

costs that would be projected by lifecycle cost analyses that fail to consider the impact of inflation and price volatility. What's more, the disparity between the life-cycle costs between concrete and asphalt shifts dramatically in favor of concrete when the life-cycle cost analysis accounts for inflation. However, the National Asphalt Pavement Association (NAPA) has responded by stating that applying a material-specific discount rate is not accepted as valid by the economics profession. Also, using historical price inflation data to predict future prices is an unsupported methodology. Standard economic practices caution against trying to forecast future price trends for inflation or highly volatile commodities, such as oil, over periods of time longer than six months. Beyond these economic flaws, the Concrete Sustainability Hub's report ignores innovations in asphalt engineering already being used to reduce project costs, such as the use of warm-mix asphalt and reclaimed asphalt pavement. *Picture Courtesy: www.basf.com

DCS Trading & Services Pvt.Ltd

Concrete Durability

Mechanisms of Deterioration of Reinforced Concrete Structures

Dr. Manu Santhanam Associate Professor, Department of Civil Engineering, IIT Madras

D

urability of hydraulic-cement concrete is defined as its ability to resist weathering action, chemical attack, abrasion, or any other process of deterioration (ACI). Durable concrete will retain its original form, quality, and serviceability when exposed to its environment. Concrete is an inherently durable material. Reinforced concrete structures are expected to be maintenance-free during their service lives. However, there is evidence of premature deterioration of modern structures. The resultant costs to the economy reach 3 - 5% of GNP in some countries (and up to 50% of construction budgets). This occurs because existing knowledge not adequately applied. As shown in Figure 1, durability of concrete depends on two primary factors - the concrete system, and the service environment. The concrete can be further subdivided into the materials and the process, while deterioration in service conditions can be through physical or chemical means.

Concrete has to function in different types of environments, some of which are aggressive or degrading to the concrete quality. Typical aggressive environments are: Seawater (or close to sea), Polluted soils (due to industrial or agricultural effluents), Freezing conditions, to name a few. Design of concrete for these environments has to take into consideration the alterations that cement paste (or concrete) may undergo upon interaction with the environment. The common durability problems in concrete are: -

Corrosion of steel in reinforced concrete Sulphate and other chemical attack Alkali aggregate reaction (more of a material problem than environmental) Freezing and thawing damage Carbonation

Concrete characteristics affecting performance Porosity and permeability Durability of concrete is related to its performance in the service environment. Concrete is subjected to a host of durability problems, which typically result in:

Figure 1. Constituents of concrete durability

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-

Progressive loss of mass from the surface

-

Volume changes, which can be of three types: (1) both paste and aggregate expand, (2) the paste expands, while the aggregate is inert, or (3) only the aggregate expands.

Water is common to all the durability problems in concrete. The presence of water, or its involvement in the reactions is necessary for the problems to occur. Thus, the durability of concrete is intrinsically related to its watertightness, or permeability.

Concrete Durability

Permeability of concrete is a function of the permeability of the cement paste, of the aggregate, and of the interfacial transition zone. The permeability of these components is in turn related to the porosity. Paste capillary porosity is typically 30 - 40%, while normal aggregates have a porosity of 2 - 3% (and rarely greater than 8 - 10%). The transition zone is highly porous due to the presence of flaws such as microcracks and bleedchannels.

Figure 2. Porosity and permeability: A is highly porous compared to B, but probably less permeable due to the poor interconnectivity of pores

Mix characteristics - w/c and presence of admixtures Both porosity and permeability increase with an increase in the water to cement ratio. The permeability also depends on the degree and nature of curing, and the presence of mineral admixtures, which can act as fillers densifying the transition zone. Additionally, the pozzolanic reaction of mineral admixtures contributes to the resistance of concrete. Chemical admixtures such as corrosion inhibitors and air entraining chemicals enhance the performance of concrete during corrosion and freezing, respectively. Type of cement and aggregate Blended cements perform better (combined benefits of pozzolanic reaction and reduced permeability) in all environments. Special cements such as Type V (sulphate resistant) and Sulpersulphated cement are good for sulphate resistance. As far as aggregates are concerned, low density material is susceptible to freezing damage. The bond with cement paste will govern the quality of interfacial zone. Some aggregates have better bond than others.

Importance of the cover zone The importance of a good concrete cover for reinforcing steel cannot be overemphasized. The cover concrete is primarily responsible for its response to the service environment. Sulphate attack on concrete Sulphate attack is the deterioration of concrete by means of reactions between sulphate ions and hydrated cement products. Generally, sulphate attack is divided into two categories: External and Internal. External sulphate attack is when the source of sulphate ions is external to the concrete, such as when it is from ground water or seawater. Na 2 SO 4 , MgSO 4 , CaSO 4 and (NH 4 ) 2 SO 4 are some detrimental sulphate sources that are primarily found in ground water contaminated with industrial effluents and agricultural products. Internal sulphate attack, on the other hand, occurs when a late release of sulphates within concrete takes place. In this case, the formation of ettringite occurs after the concrete has hardened, and this results in distress. Sodium sulfate (N ) and magnesium sulfate (M ) can react with CH to produce gypsum (C H2), sodium hydroxide (NH) and magnesium hydroxide (MH, or brucite). It is not fully understood if gypsum formation causes any volumetric expansion. The formation of gypsum, however, is reported to render the structure soft, which leads to a decrease in strength of the structure. The formation of gypsum is closely linked to the formation of other products of sulfate attack, as gypsum can combine with other hydration products to produce ettringite. This phenomenon is called ettringite corrosion. The formation of ettringite is said to be expansive, although the mechanism of expansion is still debated by researchers. Numerous theories have been postulated to explain the expansion due to ettringite formation: (1) crystal growth, either by topochemical (when the products form at the reactant sites itself) mechanism, where ettringite crystals grow on the surface of aluminate particles, or by throughsolution mechanism; (2) swelling due to imbibition of water, because of the high surface area of ettringite.

Presence of cracks

The damaging effects on the C-S-H gel are only due to the action of magnesium sulfates.

Cracks in concrete could be structural or non-structural (thermal effects, shrinkage etc.). Most often, the nonstructural cracks occur as a result of poor material selection, lack of adequate quality control, etc. There is no use having HPC between cracks, since cracks will serve as channels for the ingress of water and other chemicals. Good concreting practice is the only way to minimize unwanted cracking.

The MH and the silica hydrate (SHy) formed in this reaction further react to produce magnesium silicate hydrate (MS-H), which is reported to be non - cementitious, and leads to complete disinitegration. The phenomenon of progressive reduction of the C/S ratio within the C-S-H gel is called decalcification. This process does not actually begin until the pH drops to very low values (<10).


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Concrete Durability

The conversion to M-S-H is a very advanced stage of deterioration. The M-S-H and gypsum formed from the above reactions are frequently observed to be deposited in bands parallel to the exposed surface. The decomposition of the C-S-H gel into a non-cementitious M-S-H can be achieved only by M . The decomposition by the M doesn't stop with the formation of M-S-H but continues further. The action of M renders a low pH to the

pore solution. Hence the C-S-H releases some CH into the solution in order to stabilize itself at a higher pH. But since there is M in the surrounding environment, the deterioration cycle repeats itself beginning with the gypsum corrosion.

Figure 1. Cement mortar in sodium sulphate solution showing deposition of ettringite (E) in the cracked surface zones; the dark region represents decalcified C-S-H

Figure 3. Layer of gypsum surrounding sand grain in cement mortar stored in sodium sulphate solution, suggesting a conversion of CH to gypsum; small deposits of ettringite are also visible

Figure 2. Large deposit of gypsum formed in cement mortar in sodium sulphate solution

Figure 4. Layers of M-S-H and gypsum on the surface of concrete subjected to magnesium sulphate attack

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Some scanning electron micrographs that depict the attack of cement mortars by sodium and magnesium sulphate solutions are presented below in Figures 1 - 6.

United Steel & Structurals Pvt. Ltd

Concrete Durability

content that can cause corrosion. Thus, a moderate C3A content should be prescribed in such cases. Lowering of C3S might also help, since this would reduce the amount of CH that forms. -

The best protection against sulphate attack is to have a low w/c in concrete. Blended cements, that lead to a consumption of CH, need not be good in cases of magnesium sulphate attack.

-

Use of high alumina cement: HAC is good for sulphate resistance if the conversion of its hydration product does not occur.

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Supersulphated cement: In this cement, all the available aluminates are converted to ettringite during hydration. Thus, there are no excess aluminates present to react with external sulphate ions.

Sea water attack Figure 5. Formation of a surface double-layer of brucite(B) and gypsum(G) in a cement mortar stored in magnesium sulphate solution

Sulphate attack can also take place in seawater. However, the mechanism may be altered due to the presence of a high concentration of chlorides. Typically, seawater attack is characterized by the formation of higher amounts of brucite compared to groundwater attack. In addition to the chemical reactions involved in sulphate attack, physical deterioration of the concrete may also occur due to cycles of drying and wetting. The tidal zones in concrete structures are especially susceptible to alternate drying and wetting, which may lead to the crystallization of salts in the surface pores, and the development of expansive pressures that may cause spalling. The action of waves can further aggravate the surface concrete. Acid attack

Figure 6. M-S-H and gypsum in a highly deteriorated surface zone of a cement mortar stored in magnesium sulphate solution

Attack by sulfuric acid occurs most commonly in sewers, where a lot of sulphide gases exist owing to the large degree of microbial action. Sulfuric acid creates an acidic environment in the concrete, in which the primary cement phases (C-S-H, ettringite) are extremely unstable. Gypsum formation occurs when sulfuric acid reacts with CH. The loss of integrity and softening of the structure occur as a result of gypsum formation and destabilization of C-S-H.

Protection from sulphate attack

Carbonation

" Use of low C3A cements: The philosophy of prescribing low C3A cement to improve resistance to sulphate attack hinges on the need to minimize ettringite formation after the concrete hardens. When the C3A content is low, most ettringite will be formed in the plastic state. The use of very low C3A content, however, is not good in the case of attack by chlorides. C3A can bind the chlorides that penetrate into concrete, thus reducing the free chloride

Carbon dioxide diffuses into the pores of concrete and reacts with calcium hydroxide; as a result, the alkalinity (pH) of the concrete is reduced. Reduction of pH causes the passivity of reinforcing steel (protective layer) to be destroyed.

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Delayed Ettringite Formation (DEF) Under certain initial storage or curing conditions, such as

Concrete Durability

for steam-cured concrete that is subjected to high temperatures, the ettringite that forms in the process of cement hydration gets destroyed. The formation of ettringite in the early stages may also not occur if there is a late release of sulfates. The reformation of ettringite in hardened concrete in the presence of moisture leads to the generation of expansive pressures, and cracking of concrete. This is called delayed or secondary or late ettringite formation. Most researchers believe that three elements are essential for DEF to occur: presence of microcracks, late sulfate release, and exposure to water. If cracks are present in concrete, DEF causes the deposition of ettringite in the cracks. The late-released sulfates, or the sulfates from the deteriorated ettringite, go into the structure of C-S-H. These are released later by moisture, which carries them to the aluminate phases, resulting in the formation of ettringite. This ettringite often effectively masquerades as ASR, since it forms in extremely small crystals. DEF is more of a problem with modern cements, since the clinker SO3 levels have increased dramatically over the years, and the use of sulfur fuels has also grown. Thus, it is all the more essential nowadays to restrict the temperature rise in concrete, not only from steam curing but also from the use of rapid hardening cements. Most European countries have adopted standards restricting concrete temperatures. Alkali aggregate reaction Many siliceous igneous (opal, chalcedony) and sedimentary rocks (chert) possess a glassy or amorphous texture. In alkaline environments the silica structure can get dissolved from these aggregates. The resultant reaction between silica and alkalis results in the formation of a gel that is expansive. This phenomenon is called the alkali-silica reaction. Strained quartz present in metamorphic rocks may also be susceptible to damage by alkali-silica reaction (ASR). The alkalis may come from the cement, chemical and mineral admixtures, impurities in aggregate or water. The reaction itself needs the presence of moisture.

(Na+ or K+) in the gel determines its expansive nature. Usually, the higher the Ca2+, the lesser expansive the gel. If the alkali hydroxide concentration falls below 0.3N, the reaction tends to slow down and stop. The rate of reaction cannot be determined from the amount of gel forming, since it does not have a distinct composition. The amount of expansion in ASR depends on the type of aggregate. For some aggregates, a pessimum type relation is observed between the % expansion and the % of reactive aggregate, while for others, the % expansion increases consistently with an increasing proportion of reactive aggregate. The decrease of expansion beyond a certain limit occurs because when there is too much reactive silica, the gel can form at very early stages when the concrete is still in the plastic state. At high alkali contents, the gel that forms has got a low viscosity, and is thus not able to generate high expansive pressures. In the case of aggregate size, when the size is too small, the reaction occurs in the plastic state of concrete, and thus does not lead to any expansion. On the other hand, for very large aggregates, the surface area to volume ratio becomes too small for the reaction surface to be a significant factor. Mechanism of expansion Various theories have been proposed to account for the expansion that occurs as a result of ASR. These are: -

Absorption (swelling) theory proposed by Vivian: The imbibition of pore water and the resultant swelling of the alkali-silica gel causes expansion. The aggregate grows outward and puts the paste in tension.

-

Osmotic pressure theory proposed by Hansen: The alkali-silica gel acts as a semi-permeable membrane that allows only an inward diffusion of OH-, Na+, K+, and Ca2+ from the pores to the aggregate surface. Thus the aggregate exerts osmotic pressure against the surrounding paste. Lea modified this theory and stated that there is actually a preferential diffusion of some species - Na+, K+ - over others such as Ca2+.

Manifestation of ASR

The first step in this reaction happened on the surface of the aggregate, where the Si-O bonds are dissolved by OH-. Thus, the silica becomes available to combine with the alkalis to form alkali-silica gel.

ASR is a very slow reaction and may take many years to show up at the surface of the concrete and get detected. Cracking due to ASR generally shows up as a map pattern on the surface. Irregular small cracks form at the surface. These are unsightly, but are rarely the cause of a structural collapse. However, expansion associated with ASR can cause misalignments.

The alkali silica gel formed from the above reaction could also contain some Ca2+. The ratio of Ca2+ to the alkalis

Surface aggregates can often pop out of the concrete due to expansion. The alkali-silica gel can ooze out to the

SiO2 + KOH (in the presence of moisture) gel (no definite composition)

→Alkali silica


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Concrete Durability

surface and get carbonated if wet. The resultant hard white gel that forms resembles carbonated calcium hydroxide. Microstructurally, reaction rims are often visible on the surface of reactive aggregates due to a slow dissolution of the silica. However, the rim could also be due to weathering, Certain ASR reactive aggregates even do not form rims. Protection against ASR Due to circumstances, it is not possible to change an aggregate source locally even if prior knowledge about the reactivity of the aggregate is available. Thus, other methods have to be adopted in order to prevent ASR. The primary measures for protection are: -

Use of low alkali cement (< 0.6% equivalent Na2O).

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Preventing access of moisture.

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Using coatings (such as silane, which allows water vapour to go out of concrete, but does not permit water to come in) or waterproofing agents.

-

Use of chemical admixtures such as Lithium salts (LiNO3, LiOH, etc.) or alkyl alkoxy silanes, which bind the reactive silica into a non-expansive product.

-

Use of mineral admixtures such as silica fume. Mineral admixtures can act in two ways: (1) by reducing the penetration of water, and (2) by binding the alkalis within the unhydrated glass. The alkali silica gel that forms in mineral admixtures is also high in Ca2+, and is thus not very expansive.

Freezing and thawing related damage The damage due to freezing and thawing (F/T) is a physical problem, unlike the chemical issues that were discussed earlier. F/T can cause three types of failures: -

Paste failure: This is related to the failure of the paste. Parallel cracks form in the paste and proceed inward from the places where concrete first becomes highly saturated with water. Sometimes, scaling of the top surface can occur. Scaling is exacerbated when deicing salts are used.

-

Aggregate failure - D-cracking: This relates to the failure of the paste when it is subjected to expansive stressed by the aggregate. It shows up as parallel cracks proceeding inward from the point of saturation. The pattern of cracking on a jointed concrete pavement or slab appears like the letter D, as shown in the figure below.

-

Aggregate failure - popout: Popouts are caused when porous aggregates on the surface of concrete are

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Figure 7. D-cracking in a concrete pavement slab

subjected to expansion on freezing. A part or the whole of the aggregate piece cracks and pops out. Sometimes, a mortar flake can also pop off as a result of the expansion of an underlying aggregate. Mechanism of freezing and thawing Water expands by 9 - 10% upon freezing. Thus, the critical saturation of a pore in concrete is about 90%. It must be understood that freezing point in small pores is depressed to a large extent. In fact, in some of the small pores in concrete, freezing does not occur until temperatures as low as - 40 oC. Also, the presence of other ions in the pore solution also depresses the freezing point. If the concrete remains frozen through its lifetime, then not much of a problem occurs. The deterioration occurs only if there are successive cycles of freezing and thawing. The expansion and damage associated with F/T is explained using various mechanisms. Let us first consider the case of paste failure (see Figure 8).

Figure 8. Movement of water inside capillaries

STP Ltd

Concrete Durability

Water in the large pores near the surface of the concrete is the first to freeze. The freezing of concrete proceeds in a front parallel to the surface. The expansion of water in the large pores on freezing drives out the unfrozen water into the paste. The travel of water through the paste generates a hydraulic pressure. The longer the path of flow of water, the higher the pressure generated. If the flow path is longer than a critical distance (0.2 mm for concrete) then failure occurs. The use of air entraining agents is the best remedy for paste failure. Air bubbles serve as closely spaced reservoirs into which the unfrozen water can migrate. The spacing between air bubbles should be smaller than twice the critical distance (0.2 mm) for the air entrainment to be really effective. Thus, it is not just the amount of air entrained, but also the dispersion of air that is important. The larger the coarse aggregate size, the lower is the air entrainment required. When high strength concrete with low w/c is used, the pore size can be so small that freezing does not even occur at service temperatures. Thus, air entrainment is sometimes not necessary in such cases. The use of mineral admixtures, which act as pore refiners, can thus be beneficial. However, mineral admixtures tend to increase the scaling problem in concrete. In the case of aggregate failure, the type of failure is dictated by the porosity of the aggregate. If aggregate porosity if very high, then the expansive stresses generated by the aggregate are not critical. In other words, the expansion is accommodated by the aggregate elastically. Popouts are caused by aggregates that have a moderately high porosity. Such low-density aggregates (cherts are especially susceptible) are subjected to high internal pressures due to expansion. The problem gets worse when the aggregate size is large. The remedy is to screen the concrete aggregate for low-density elements. In the case of D-cracking, the aggregate porosity is not high. Thus, and expansion of the water in the aggregate causes the unfrozen water to move into the surrounding paste, resulting in hydraulic pressures. Air entrainment of the paste can help in this case to a certain extent.

and the cathode reaction, as shown in Figure 9. An electrical current flows through the aqueous medium

Figure 9. Reactions of corrosion

Figure 10. Current flow during corrosion process

opposite to the direction of flow of the electrons (see Figure 10). In addition to the electron current, there is also an ionic current. The flow of current resembles a battery cell. This system is thus known as a 'galvanic cell' and the process is also known as 'galvanic corrosion'. The ferrous and hydroxyl ions combine to form the rust products. 2 Fe2+ + 4 OH- → 2 Fe(OH)2 (greenish rust) The greenish rust, upon further reactions with O2 and OH, can form Fe2O3 (red rust) and Fe3O4 (black rust). The rust often accumulates at places other than the reaction sites. Likelihood of occurrence of corrosion Anodic sites can be created on steel due to a multitude of reasons:

Corrosion of reinforcing steel The corrosion of steel in reinforced concrete is a problem of mammoth proportions. It is estimated that 5% of a developed nation's GDP is utilized for repair of corrosionrelated damage. The yearly cost of repairs for reinforced concrete bridge decks in the US alone is estimated to be $ 50 - 200 million. Corrosion is an electrochemical problem. The overall mechanism can be broken up into the anode reaction

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-

Compositional variances on the steel surface

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Presence of dust/dirt etc. partially on the steel surface

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Presence of local differences in applied stress

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Microstructural variations in the steel: (1) The ferrite phase is more active than the cementite phase, (2) Grain boundary atoms are more active compared to the bulk

-

Strained zones produced during cold working of

Concrete Durability

produces a significant reduction in the potential difference between the anodic and cathodic areas. This phenomenon is called 'concentration polarization'.

metals may be more active -

Presence of stress concentrations

-

Differences in oxygen concentration at different sites on the steel: generally, the site with a lower oxygen concentration becomes anodic

Figure 11. Rust formation and delamination of concrete

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Resistivity of the medium (concrete and its pore solution): The flow of ions has to occur through the medium of concrete and the pore solution. Thus, the resistivity of the concrete can have a significant bearing upon the easy flow of ions.

-

Passivation of steel: In an alkaline environment, the surface atoms of the steel get oxidized to form an thin oxide layer (thickness of about 10 nm). This film is stable at the highly alkaline environment of concrete. The stability of the film is enhanced when the steel contains a large amount of alloys. This phenomenon of the formation of a protective layer around the steel is called 'passivation', and is made possible by the high concentration of OH- in the concrete pore solution. The level of OH- required to maintain passivation is not a constant value, but depends on the presence of other ions, especially Cl-. The ratio of OH- to Cl- is very important. Depassivation can occur by a number of mechanisms: (1) Consumption of OH- by carbonation and other reactions; when the pH falls below 11.5, the film is no longer stable; (2) Presence of a high concentration of Cl-: In addition to lowering the pH due to ionic balance with OH-, Cl- can react with oxide films of Fe(OH)2 (that have not been converted to the

Figure 12. Relative volumes of corrosion products

Manifestation of corrosion -

-

Formation of rust causes expansion and cracking (some forms of rust are 6 - 7 times the volume of undamaged steel) - see Figures 11 and 12. Loss of sectional area of rebar - reduction in load carrying ability

Factors controlling the rate of corrosion The following are the principal factors that control the rate of corrosion: -

Availability of dissolved oxygen and moisture at the cathode: In order for the cathodic reaction to occur, both oxygen and moisture are necessary. Due to the concrete cover, both these elements have to reach the steel surface by diffusion. This slow diffusion

Figure 13. Some factors governing the rate of corrosion

stable oxide film because of lack of availability of oxygen) to form iron chlorides. This results in pitting corrosion. A threshold concentration of Cl- has to be exceeded before corrosion can take place, and this concentration is a function of the OH- concentration or pH. Limits on Cl- concentration have been stipulated in various codes. Figure 14 shows the rate of occurrence of corrosion. As shown in the figure, the initiation stage lasts until the depassivation of steel. Beyond this stage, the propagation of corrosion occurs at an almost constant rate. Finally, the corrosion process enters an acceleration stage where the rate is high.


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Concrete Durability

supplied to the steel to keep it cathodic and preventing oxidation from occurring. -

Use of stainless steel (very high Cr): Produces a stable passivating film.

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Use of epoxy coated steel.

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Use of corrosion inhibitors (see chapter on Chemical Admixtures).

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Adequate depth of cover.

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Good quality concrete with low permeability.

Summary

Figure 14. Rate of corrosion

Protection mechanisms against corrosion -

-

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Galvanization: this process involves the plating or steel with Zinc. Zn, having a higher electrochemical potential compared to Fe, becomes the sacrificial anode, and Fe is protected as the cathode. Cathodic protection: An external voltage or current is


Good concrete performance in aggressive environments can only come about with the combined action of a number of factors: -

Proper mix design

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Reduction of cracking

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Optimum cover thickness

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Adequate compaction and curing

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Quality of construction

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Correct maintenance

Esquire CMAC Pvt.Ltd

Corrosion Reinforcing Steel

Corrosion of Steel in Concrete & Assessment Techniques

George Sergi, Ph.D Technical Director, Vector Corrosion Technologies

Concrete is a porous material whose pores contain an electrolyte made up primarily of sodium and potassium hydroxides.1Steel reinforcement is normally protected in such an electrolyte owing to the formation of a dense and uniform passive oxide film.2 Carbonation of the concrete (neutralisation of the alkali constituents by CO2 gas from the atmosphere), or infestation of the concrete with salt from seawater or from deicing agents leads to the breakdown of the protective oxide film and to corrosion of the steel.3,4 Corrosion of steel in concrete is an electrochemical process whereby anodic and cathodic reactions occur simultaneously on the surface of the steel resulting in the dissolution of the metal at the anodic sites.5 The corrosion cell To demonstrate the principles of electrochemical corrosion, let us consider the simple "Daniel-cell". This consists of zinc immersed in ZnSO4 solution and copper immersed in a CuSO4 solution. The two electrodes are connected to a variable resistor R, voltmeter V, and ammeter A (Fig, 1). The potential difference (emf) between the two electrodes when no current is flowing is 1.1 V. If a small current is allowed to flow through the external resistor (I1 in Fig. 2), the measured potential difference falls below 1.1 V because both electrodes polarise, Zn to b and Cu to e (Fig. 2). As the resistance is decreased, the current increases and the potential difference decreases until, when the system is short-circuited (the resistance is very small), maximum current flows and the potential difference is almost zero (Imax ). The Zn anode polarises along the line abc and the Cu cathode along the line def. The full polarisation of Zn in volts is given by c-a and for Cu by f-d.

Iron atoms undergo oxidation (electron loss) to form F++ ions which pass into solution. The excess free electrons left in the metal are consumed, converting oxygen and water to hydroxyl ions in a process of reduction (electron addition) according to the following cathodic reaction: ½ O2 + H2O + 2e- → 20H Both the anodic and cathodic reactions occur at adjacent

The anodic reaction in the "Daniel-cell" is: Zn → Zn2+ + 2ewhere Zn corrodes and goes into solution and the cathodic reaction is: Cu2+ + 2e- → Cu where copper is deposited from the CuSO4 solution. In the case of steel in oxygenated water, the simplified anodic reaction is: Fe→ Fe2+ + 2e-

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Figure 1 Polarised copper-zinc cell (Daniel-cell)


point of intersection in Figure 4. Faraday's laws of electrolysis may be used to obtain corrosion rates in more familiar terms (average rates of mass loss per unit area) and these values may be simply converted to average rates of loss of thickness of metal from knowledge of the density of the steel.

Figure 2 Polarisation diagram for copper-zinc cell

sites simultaneously on the surface of the steel (Fig. 3). As was the case with the "Daniel..cell", the nodic and cathodic reactions of steel in water can be represented in a polarization diagram (known as an "Evans" diagram), as shown in Fig. 4. The intersection point of the two lines corresponds to the electrode potential at which the rates of the anodic and cathodic reactions are equal and is termed the corrosion potential, (Ecorr), the value that steel adopts when corroding freely. The magnitude of the anodic and cathodic reactions is represented by the number of electrons flowing per second between the anodic and cathodic sites on a unit area of the metal surface and is a measure of the corrosion rate, Icorr. It is often referred to as the corrosion current density and expressed in electrical units (amps/m2 of steel area or more commonly, mA/m2 ). It is the current at the equivalent

Figure 3 Mechanism of corrosion in oxygenated water

Figure 4 Evans diagram for iron corroding in oxygenated water

Factors affecting corrosion rates Both Icorr and Ecorr can vary depending on the degree of polarization of either the anodic or the cathodic reactions. When polarisation occurs mostly at the anodes, (i.e. the anodic process is for some reason hindered) it is said that the corrosion reaction is anodically controlled. Similarly, if the cathodic reaction is polarised, the corrosion reaction is said to be cathodically controlled. Since the operation of a corrosion cell depends on three processes occurring in series, viz. the anodic reaction, the cathodic reaction and the flow of currents through the intervening electrolyte and metal the overall corrosion rate is not only governed by the anodic and cathodic reactions but also by the magnitude of the resistance of the electrolyte which can hinder ionic conduction. This is represented graphically in Figure 5. Corrosion of steel in concrete When steel is immersed in an alkaline solution such as sodium or potassium hydroxide, its surface becomes coated with an adherent, insoluble oxide film (γ-Fe2O3) which is stable over a range of potentials. Its polarisation curve is modified to that shown in Figure 6 and shows that the corrosion rate over intermediate potentials becomes very small.6 Such a situation is termed passivity, one of the states in which the metal can thermodynamically exist at variable pH levels of the electrolyte as shown by a simplified Pourbaix


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no longer be thermodynamically stable and the steel corrodes as it would in an equivalent neutral solution (Fig. 4). The rate of steel corrosion in carbonated concrete is subject to anodic resistance control.78, It therefore depends critically on the moisture content of the concrete since this is primarily what determines the electrolytic resistivity of the material. The corrosion potential of the steel in this condition is typically in the range -450 to 600mV (CSE scale) when corrosion is occurring.

Figure 5 Effect of resistance of the electrolyte on the corrosion rate of the reinforcement

diagram for steel (Fig. 7). The pore electrolyte of concrete is primarily a mixture of sodium and potassium hydroxides and as such, the embedded steel attains passivity. The condition is usually characterised by a value of Ecorr higher than about -250mV (measured relative to a standard copper/ copper sulphate reference electrodeCSE scale). When carbonation of the concrete occurs, whereby the pH of the pore electrolyte becomes neutral, passivity can

Figure 6 Evans diagram for passive iron in oxygenated alkaline solution

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Figure 7 Pourbaix diagram for steel

The other main cause of corrosion of reinforcing steel is the presence of chloride salts in the concrete. In sufficient concentrations, they can undermine the passive film of the steel locally and bring about pitting corrosion. This is illustrated by a modified Pourbaix diagram (Fig. 8) and by a series of polarisation scans of steel in concrete contaminated with chloride (Fig. 9). It is evident from Figure 9 that the corrosion potential becomes more negative and the corrosion rate increases as the chloride concentration increases.

Figure 8 Modified Pourbaix diagram for steel in solutions contaminated with chloride

Zamil Steel Buildings India Pvt.Ltd


chlorides are suspected, dust samples should be collected from selected nodes on a grid at increasing depths into the concrete. This can be done simply with the use of a drill. A concentration gradient of chloride would suggest that the source was external (deicing salts, seawater) whereas a fairly constant concentration may suggest that the chlorides were added to the concrete at the mixing stage. The depth of carbonation (neutralisation of concrete alkalinity by acidic gasses such as CO2) can be determined by spraying phenolphthalein indicator either on freshly broken concrete or on drilled powder at increasing depths. Potential mapping

Figure 9 Evans diagram for steel undergoing pitting corrosion in chloride contaminated concrete

Durability assessment and corrosion detection of steel reinforcement There are a few obvious and simple techniques that should be carried out initially in order to obtain an overall picture of the condition of the reinforced structure. A good visual survey is probably the most important step in the assessment. It is essential to visit the site and look for telltale signs such as cracking of the concrete, rust staining, delamination but perhaps more importantly, signs of water retention, inadequate drainage and, particularly in flat surfaces such as car parks, formation of paddles. Edges and crevices should be studied carefully. An assessment of possible environmental factors such as exposure of structure to direct rainfall, sun and wind should be made. Then, key regions that may require detailed investigation can be selected.

It was shown above that the potential of steel reinforcement can give a good indication of its condition. Potential mapping is used, therefore, as a major investigative technique for the detection of steel reinforcement corrosion. The set-up for carrying out a potential map is simple and it involves a few easy steps. First of all, electrical continuity of the reinforcement is checked by measuring the resistance between two points where the steel has been exposed. A resistance of less than 1Ω would normally signify continuity of the steel. The potential on the steel is then measured relative to a

Chloride and carbonation survey As was discussed earlier, both carbonation and chloride infestation can lead to corrosion of the reinforcement. If

Figure 10 Simple potential mapping set-up

Figure 11 Potential map of concrete section showing several areas of low potential / high corrosion activity

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standard reference electrode (normally copper/copper sulphate or silver/silver chloride) by resting the reference electrode on the appropriate position on the surface of the concrete as shown in Figure 10. A potential map can then be constructed (Figure 11) which can show equipotential contours on the surface of the concrete. Regions of high corrosion activity can normally be identified as they show characteristically low potentials. It is generally assumed that the probability of corrosion of the steel reinforcement increases as the potential diminishes. There is, however, a lot of uncertainty in the middle range of potentials (-200 to -350mV). The problem arises primarily from the way the potential of the steel reinforcement is determined in practice. Figure 12 shows diagrammatically the current distribution around a corroding site (the anode) through the surrounding concrete to the adjacent cathode regions. These constant current flux lines, give rise to equipotential lines distributed through the concrete as shown in Figure 12. In a region above the anode the "apparent" potential is Ea (Fig. 12) and at some distance away at the cathode it is Ec. The value of Ea is normally less (more -ve) than that of Ec so local corrosion sites can be identified. It can be seen, however, that the potential measured on the surface is not necessarily that of the anode. This "surface" potential is influenced by parameters such as the concrete cover depth and the resistivity of the concrete which can alter the constant current flux lines and subsequently the equipotential lines. Wetting of the concrete will inevitably reduce the resistivity of the concrete and therefore change significantly the potential characteristics.

mapping, when used on its own, can provide a reasonable assessment of the corrosion activity of the reinforcement at the time of the survey. It cannot, however, provide information on the rate or extent of corrosion.

Figure 13 Evans diagram for passive steel in uncontaminated concrete containing different concentrations of oxygen

Resistivity measurements As was shown earlier (see for example Fig. 5), the resistance of the cover concrete can have a significant effect on the corrosion rate of the reinforcement. The rate of corrosion at the anode is dependent on the ease with which ions can pass through the concrete pore electrolyte between the cathode and anode. Hence a large potential gradient between the anode and cathode associated with a low concrete resistivity will normally signify a high corrosion rate of the reinforcement. The 4-point Wenner technique, developed from its use in geotechnical surveying, is a technique that can measure the resistivity of concrete. It involves passing an alternating current between the outer pair of four equispaced probes in contact with the concrete surface, as shown in Figure 14. The resistivity of the concrete can be calculated from the measured voltage between the inner probes from:

Figure 12 Current and potential distribution in concrete near anodic corrosion

Where, a, is the spacing between the probes.

A further complication which gives rise to a common misunderstanding, is the fact that steel embedded in submerged or waterlogged structures can exhibit potentials which are more negative than -0.35 V (CSE scale) whilst suffering negligible corrosion. This is caused by the inability of oxygen to penetrate the cover depth in sufficient quantities which leads to the polarisation of the cathodic reaction as shown in Figure 13. Provided the condition of the concrete is taken into account, potential

The resistivity of the concrete will normally be affected by many factors including moisture and salt content of the concrete, mix proportions, water /.cement ratio, type of cement replacement etc. As a general rule, if the resistivity of the concrete is lower than 10,000 Ωcm, the corrosion rate of the reinforcement which is suspected from a potential mapping survey to be corroding, is likely to be high. Higher resistivity values would normally signify a lower corrosion risk.


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In theory, it should be possible to estimate fairly accurately with the use of computer modelling the corrosion current of steel reinforcement from a combination of potential mapping and resistivity measurements. In practice, there are, however, limitations as to the accuracy of the obtained potential values, as was shown earlier, and of the resistivity values owing to the inhomogeneity of concrete. Increasing the spacing between the probes will diminish the effects of localised non homogeneity but there is a limit determined by the concrete cover depth as the highly conductive steel provides an easy path for the input current. Furthermore, resistivity on the surface layer of the concrete is different to that of the bulk owing to curing effects, differential wetting or drying and particularly carbonation of the surface layer. It is common practice to drill shallow holes at the positions where the probes will be located so that these surface effects are minimised.

connected and the true area of the steel being polarised during the test is difficult to establish. Recent developments10 have attempted to concentrate the polarisation over a small calculated area of the steel reinforcement with the use of a special anode arrangement (Figure 15) but problems are always likely to exist because of variations in the concrete cover depths, the geometry of the structure and the distribution of the steel reinforcement bars.

Linear polarisation techniques The actual corrosion rate of a section of steel reinforcement can be determined by linear polarisation. The technique essentially involves shifting the corrosion potential of a known area of steel reinforcement in either the positive or negative direction with the use of a potentiostat and measuring the current that flows between the steel and an external auxiliary electrode placed in close proximity to the steel and in contact with the concrete via the potentiostat. This can be done in single steps of potential shifts or by scanning the potential over a range of typically ± 20mV with respect to the corrosion potential.8 The increase in current at such a small shift in potential is essentially linear and the gradient of the current- potential plot gives the polarisation resistance, Rp, which can be related to the corrosion rate by the Stern and Geary equation:

Figure 15 Arrangement of insitu linear polarisation device

Final assessment A combination of the assessment techniques described above, should give a fair indication of the present condition of the reinforcement. They do not, however, show how the corrosion varies with the change of environmental conditions. That information can be obtained by frequent visits to the site or by continuous monitoring with the use of embeddable reference electrodes and other probes. Neither do they reveal the extent of the corrosion and the length of time that corrosion had been occurring. Figure 16 describes the different stages of the corrosion process. There is a virtually corrosion-free period before initiation occurs (a), followed by a period of corrosion propagation (a-b) before the reinforced structure totally loses its serviceability. A survey of the kind described earlier can

where βa and βc are the anodic and cathodic Tafel slopes respectively.The slopes can be determined experimentally but they are normally assumed to be about 120 mV/decade so that the above equation is simplified to: Rp = 26 / Icorr As the corrosion rate can vary by several orders of magnitude such an assumption is acceptable and will only introduce comparatively small errors in the calculated corrosion rates. Laboratory work has shown that corrosion rates of steel in concrete calculated in this way are in good agreement with weight loss determinations of the same steel.9 The biggest limitation of this technique is the inherent difficulty of applying it to large structures where the steel reinforcement cage is electrically

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Figure 16 Stages of structural element deterioration related to reinforcement corrosion



easily detect whether you lie either before or after point a of the graph. Determining exactly where you are on the propagation stage is much more difficult and would require exposure of the reinforcement and a detailed structural assessment.

4. Hausmann D. A "Steel corrosion in concrete" Mater. Prot. 6, 1967, 19-23.

If the correct choice of assessment techniques is made, the limitations of the techniques employed are well understood and the results are interpreted wisely, it is possible to determine whether the structure is sound or whether some remedial measures are required. The assessment should also assist in the choice of rehabilitation techniques but that is practically a different discipline.

6. Page C. L. & Tteadaway K. W. J. "Aspects of the electrochemistry of steel in concrete, Nature, 297, 1982, 109-116.

References 1. Barneyback R. S. & Diamond S, "Expression and analysis of pore fluid from hardened cement pastes and mortars", Cem. &Concr. Res. 11, 1981, 279-285. 2. Arup H "The mechanisms of the protection of steel by concrete", Crane A. P. (ed), 'Corrosion of Reinforcement in Concrete Construction', Ellis Horwood, Chichester, 151-157, 1983. 3. Gonzalez A., Algaba S. & Andrade C. 'Corrosion of reinforcing bars in carbonated concrete" Br. Corros. J.,15, 1980, 135-139.

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5. Burstein Q.T. "Passivity and localised corrosion" Shreir L . L., Jarman R. A. & Burstein G.T, (eds), 'Corrosion', 3rd edn., 1994, 1.118-1.150.

7. Glass G. K., Page C. L. & Short N. R. "Factors affecting the corrosion rate of steel in carbonated mortars" Corros. Sci., 32, 1991, 1283-1294. 8. Sergi G., Lattey S. & Page C.L. "Influence of surface treatments on corrosion rates of steel in carbonated concrete" Page C. L., Treadaway K. W. J. & Bamforth P. B. (eds), 'Corrosion of Reinforcement in Concrete Construction', SCI / Elsevier, London, 1990, 409-419. 9. Andrade C. & Gonzalez J. A. "Quantitative measurements of corrosion rate of reinforcing steels embedded in concrete using polarization resistance measurements", Werkstoffe und Korrosion 29, 1978, 515-519. 10. Rodriguez J., Ortega L. M., Garcia A. M., Johansson L. & Petterson K. "On-site corrosion measurements in concrete structures" Construction Repair, Nov./Dec, 1995, 27-30

Atul Fasteners Ltd

Concrete Corrosion Reinforcing Steel

Recent Developments in Mitigation of Rebar Corrosion in Concrete

M N Ramesh, CEO Savcor India Private Limited

C

orrosion of reinforcing steel in concrete is a widespread and enormously costly problem worldwide. Numerous concrete structures including bridge decks and substructures, parking garages, balconies and others are deteriorating as a result of reinforcing steel corrosion. Virtually any reinforced concrete structure is susceptible to the ravages of corrosion if subjected to a conducive environment. The corrosion process that takes place in concrete is electrochemical in nature, very similar to a battery. Electrochemical corrosion is a phenomenon accompanied by a flow of electrons between cathodic and anodic areas on a metal surface. In concrete the electro-chemical corrosion reactions are most often triggered when three factors- chloride, oxygen and moisture-meet at the reinforcing steel surface. A sort of natural battery develops within the reinforced concrete structure, generating a low-

level internal electrical current. The points where this current leaves the metal surface and enters the concrete electrolyte are called anodes. The current leaving the concrete and returning to the steel does so at the cathodes. Corrosion or oxidation (rust) occurs only at anodes. When corrosion of reinforcing steel occurs, the rust products occupy more volume than the original steel, causing tensile forces in the concrete. Since concrete is relatively weak in tension, cracks soon develop as shown in Figure 1, exposing the steel to even more chlorides, oxygen and moisture-and the corrosion process accelerates. As corrosion continues, delaminationseparations within the concrete and parallel to the surface of the concrete occur. Delamination is usually located at, or near, the level of reinforcing steel. Eventually concrete chunks break away or spall off. Visual signs of corrosioninduced damage on many types of reinforced concrete structures are becoming more and more prevalent. In many parts of the country one can hardly drive across a bridge or enter a building that doesn't have some degree of corrosion damage! The rate of concrete deterioration at any given time is dependent on many factors including corrosion rate, reinforcing steel concentration, concrete properties, cover and the environment, to name a few. Once corrosion has begun there is one thing for certain-it will only get worse and it will do so at an ever-increasing rate (see fig.2) . Ultimately, if corrosion is allowed to continue, structural integrity can be compromised due to loss of section of the reinforcing steel and/or loss of bond between the steel and the concrete, and replacement may be the only solution. In order to mitigate or control a corrosion problem (provide low future maintenance and long term protection) specific information is needed for any given structure.

Fig.1 Cracking due to corrosion of reinforcement

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Fortunately, proven technology and scientific methods are


that are developed recently in the area of corrosion engineering. Electro chemical method of rectifying carbonation: This method is a recent development in concrete restoration. This addresses the root cause of carbonation and not its symptoms. Hence, this is a permanent solution.

Fig 2. Time dependent rebar corrosion based on various factors

available to evaluate corrosion of reinforcing steel (and other embedded metals) and associated damage on reinforced concrete structures. These techniques are designed to determine the extent of damage, define the corrosion state of steel in undamaged areas, evaluate the cause, or causes, of corrosion, and determine the potential for the steel to corrode in the future resulting in further damage. It is only after this information is obtained through a detailed corrosion condition evaluation that a suitable repair and protection specification can be developed for a corrosion-plagued structure. It is important to point out that concrete; itself can deteriorate, regardless of the condition of embedded reinforcement. Examples of this include freeze/thaw damage, sulphate attack and alkalisilica reactions. Various concrete tests are therefore often conducted as part of an overall evaluation. Although there are similarities between corrosion of conventionally reinforced concrete structures and prestressed concrete structures, this paper deals with conventionally reinforced concrete structures only, particularly with respect to the applicability of Electro-chemical protection techniques

Fig 3. Realkalisation setup for correcting corbonation of concrete

The principle of the solution is driving an alkaline solution into the carbonated concrete by an electro chemical process. It comprises of installing an external anode kept inside an alkaline electrolyte solution on the surface of the concrete. This solution can either be sodium carbonate or sodium bicarbonate. A direct current rectifier with its positive terminal connected to external anode and its negative terminal is connected to the reinforcing steel making it cathode. Upon switching on the system the alkaline solution will move inside concrete cover and will reach the reinforcing steel making the entire section and around the reinforcing steel alkaline. Thus, this process corrects the carbonation by realkalining the concrete, and forming hydroxyl ions around the steel. The schematic details of the process are illustrated in the sketch below: Electro-chemical remedial measures for Chloride Contaminated Concrete: The problem associated with the chloride contaminated concrete is pitting corrosion of rebars. The traditional methods, to remedy the problem, has been isolating the rebars from the concrete and replacing the removed concrete by a new material free from chloride such as polymer-modified mortar or micro concrete. This method however suffers the impracticability of removing concrete behind the bars and reinstating the same with new material, if a very large extent of concrete is affected by

Fig.2. Setup for desalination or chloride extraction of concrete


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chlorides. In order to overcome the above problem the recent development in the area of remediation to the chloride attacked concrete is "desalination" and "cathodic protection". These methods being electro chemical in nature address the root cause of the problem and not the symptoms. Electrochemical Chloride Extraction The Electro Chemical Chloride Extraction (ECE), extract chloride ions from contaminated concrete and is used to reduce chloride concentration near steel reinforcement to a level below the corrosion threshold. Hydroxyl ions are also generated at the reinforcement, which allows the passive oxide layer on the steel to be reformed after treatment. An externally placed anode in the electrolytic solution is connected to the positive pole and the reinforcing steel is connected to the negative pole of the rectifier. When the system is powered, all the negatively charged chloride ions will be repelled by the cathode, i.e. steel, and are forced migrate towards the anode which is place outside the concrete. These ions will be neutralized by the anode thereby extracting all the chloride ions from the concrete. This method is also known as Desalination Process. The schematic of the process setup is illustrated in fig 2 This method is recommended for the concrete structures which are located in the chloride laden atmosphere. After the process is completed, further diffusion of chloride ions in to the concrete should be prevented by providing appropriately selected protective barrier concrete surface coatings. Impressed Current Cathodic Protection (ICCP) Impressed current cathodic protection is achieved by driving a low voltage direct current from a relatively inert anode material, through the concrete to the reinforcing steel. Figure 3 shows the basic layout required for impressed current cathodic protection systems. Direct current of sufficient magnitude and polarity is applied, so as to oppose the natural flow of current resulting from the electrochemical corrosion process. The direct current is supplied by an external power source, most often a CP rectifier. Recently, the use of solar power has received attention and further research is going on for its adaptation in actual structures. Impressed Current Cathodic protection is a widely used and effective method of corrosion control. Many people, engineers included, think cathodic protection is so complicated and expensive that it has no practical use in the concrete rehabilitation industry. It is also believed that CP doesn't work or that it is unreliable in the long term. The fact is ICCP is not so complicated, is often the most cost-effective technique, and has practical application on reinforced concrete structures and that it most definitely works. Of course, performance of ICCP systems, like all other corrosion protection systems, is directly dependent on sound

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specifications, proper installation, and monitoring and maintenance. With ICCP, one cannot simply install it and forget it. Good long term performance of all ICCP systems requires good monitoring and maintenance procedures, often due to this fact is discounted as a corrosion protection system. Every corrosion protection system requires

Fig 3. Schematic of impressed current cathodic protection of reinforcement in concrete

periodic inspection and maintenance. Impressed Current Cathodic protection has been successfully used to protect pipelines, ship hulls, off shore oil platforms, heat exchangers, underground tanks, and many other facilities exposed to a corrosive environment for many decades. Its first application to steel in concrete was only in 1973. Since then, many r c structures are protected with ICCP. Recognizing that the corrosion process generates electric currents, Impressed Current Cathodic protection supplies a source of external current to counteract the corrosion current. Hence, corrosion stops, or at least is greatly minimized. After an intensive research in the areas of corrosion of steel in concrete, cathodic protection evolved as the only technique which could positively arrest corrosion of steel in existing concrete structures. In fact, cathodic protection is the only rehabilitation technique that had proven to stop corrosion in chloride affected concrete regardless of its concentration in concrete. It should be noted, however, that ICCP is not always needed nor is suitable on all structures. To select and design a proper repair and protection scheme it is imperative that the causes of the distress are properly diagnosed, fully understood, and the extent of damage is determined Hence the first step is to have a concrete and corrosion condition survey conducted in order to define the cause and extent of the problem. Electrical continuity of the reinforcing steel to be protected is also a primary factor in considering ICCP. A closed electrical circuit (unbroken electrical path) between all

Machines & Engineering Company


Element

Magnesium

Aluminium

Zinc

Chromuim

Iron/Steel

Nickel

Tin

Hydrogen

Platinum

Gold

-1.67

-0.78

-0.58

-0.44

-0.25

-0.14

0.00

+1.2

+1.80

Electrode Potential Electrode P-2.38 Table 1: specific metals in the galvanic series

reinforcing steel is required in order for the ICCP system to function properly. Electrical continuity testing can be done during the condition survey. The chloride concentration in the concrete throughout the structure is also important. If sufficient chlorides are present at the reinforcing steel depth in many areas of the structure, ICCP may be the economically viable alternative Based on the results of the condition survey determination is made on the type of repair and protection method to use. One advantage of ICCP is that removal of sound concrete is not required, thus a considerable cost savings may be realized. It may be a viable alternative to removing two or three inches of concrete over a large area in order to prevent future corrosion. Cathodic protection is usually most cost effective when long term performance is desired. Galvanic, or sacrificial anode, cathodic protection is based on the principles of dissimilar metal corrosion and the relative position of as shown in Table.1. No external power source is needed with this type of system and much less maintenance is required. Such systems also provide protective current primarily to areas on the steel surface which need it the most. However, the relatively high resistivity of concrete results in driving low voltage provided by such systems would be inadequate for cathodic protection of steel in concrete especially in the splash zones of marines rc structures subjected to drying and wetting cycles. Sacrificial anodes can be used to mitigate corrosion in certain circumstances especially for patch repair, specifically, if corrosion activity is low. In case that pitting corrosion has not initiated or propagated but in a situation prone to active corrosion, such as splash zone, a full active impressed current system is the only technically sound and cost effective option of corrosion mitigation However, if the chloride content is relatively low, or if the chlorides are generally located only in isolated areas of the structure, sacrificial anode system may be most appropriate. Basically sacrificial anode may enhance the repair work but in most cases does not deliver the protection in accordance to CP standards. So in theory it can't be called as CP. In any real corrosion problem situation where pitting corrosion has initiated and propagated, high current density, may be around 20mA/ m2 of steel surface, is required to bring the potential of rebars to certain level at which corrosion is arrested. This cannot be delivered by sacrificial anodes. Galvanized rebars The zinc on galvanized reinforcing steel functions as a

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sacrificial anode much the same way as zinc in a sacrificial anode system does. In this case, the steel is protected by the zinc from the day the rebar is galvanized. However, once all the zinc is consumed, the base steel will be susceptible to corrosion in the same way as plain reinforcing steel. Summary Reinforcing steel corrosion causes extensive damage to concrete structures. Various NDT methods are successfully employed to carryout condition survey to evaluate corrosion of reinforcing steel and the associated damage on reinforced concrete structures. These tools help in determining the extent of damage, define the corrosion state of steel in undamaged areas, evaluate the causes of corrosion and determine the potential for the steel to corrode in the future resulting in further damage. The recent development in the electro-chemical methods are aimed at addressing the cause of the problem there by ensuring a long-lasting solution to the corrosion problem. Cathodic protection is a widely used and effective method of corrosion control for reinforced concrete structures. Cathodic protection supplies a source of external current to counteract the corrosion current. Hence, corrosion stops or minimizes to a greatly low level. Almost any atmospherically exposed reinforced concrete structure or structural members of almost any geometry can be catholically protected. However, existing structures must be considered individually with regard to the need for the applicability of CP. Not all structures are good candidates for CP, but ICCP is the only system that can truly retard or mitigate corrosion in the harshest of the environment. References: -

Atef Cheaitani, M N Ramesh- Corrosion prevention considerations to achieve a 100 year design life for reinforced concrete structures in marine environments, NCCI Seminar,2010

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Atef Cheaitani, M N Ramesh- Maintaining infrastructure - the latest development in the repair and maintenance of reinforced concrete structures, Asian Conference on ecstasy in concrete 2010, Indian Institute of Technology Madras, Chennai

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Ali Sohanghpurwala and William T. Scannell -' Repair and protection of Concrete Exposed to Seawater

Action Construction Equipment Ltd

Corrosion Repair & Rehabilitation

Repair Principles for Corrosion Damaged Reinforced Concrete Structures

MG Alexander and JR Mackechnie Department of Civil Engineering, University of Cape Town

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orrosion is the inevitable process that occurs when refined metals return to their more stable combined forms as oxides, carbonates and sulphides. The corrosion process may be defined as the surface wastage that occurs when metals are exposed to reactive environments. Costs associated with corrosion damage and control can be substantial, being as much as 3.5% of the GNP of some industrial countries. Reinforced concrete structures have not been immune to the ravages of corrosion despite the protection that concrete provides to embedded steel. Reasons for the increasing incidence of corrosion damage to reinforced concrete structures include the use of deicing salts and calcium chloride set-accelerators, increased construction in aggressive environments, fast-track construction practices, changing cement composition resulting in finer grinding and lower cement contents, lower cover depths and poor construction practice including inadequate supervision. Reinforcement corrosion is particularly pernicious in that damage may occur rapidly and repairs are invariably expensive. Furthermore by the time visible corrosion damage is noticed, structural integrity may already be compromised. There is currently considerable debate about the merits of the various systems for the repair of reinforcement corrosion. This monograph attempts to clarify some of the important issues by drawing on international experience as well as local findings. Ultimately the effectiveness of repair systems should be measured in terms of cost, risk of failure and long-term performance. As such no single system is appropriate for all repairs but will depend on the type of structure, service conditions, level of deterioration and financial constraints of the project. This monograph focuses on repair principles rather than

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dealing with issues of detail that have been competently published by others. Repair options can only be rationally compared when the corrosion process and its influence on concrete are fully understood. The document also focuses on South African conditions and experiences, derived from almost ten years of research on concrete durability and repairs at the University of Cape Town. Corrosion Fundamentals Steel reinforcing bars will corrode freely when exposed to moisture and oxygen under ambient conditions. When steel is embedded in concrete however the high alkalinity (pH of 12.5 or higher) stifles corrosion by the formation of a passive ferric oxide film on the steel surface. The ferric oxide layer forms a dense, impenetrable film that suppresses further corrosion by limiting the movement of cations and anions near the steel surface. This passive ferric oxide film on embedded reinforcement may be disrupted by a reduction in the alkalinity of the concrete (principally by carbonation) or by the presence of aggressive ions such as chlorides and sulphates. Depassivation of the steel occurs as follows: -

in carbonated concrete, insufficient hydroxyl ions are available to repair pits in the passive film

-

in salt contaminated concrete, chloride ions break down the passive layer at localized pits and encourage metallic dissolution

Once depassivating conditions exist in concrete either by a reduction in alkalinity (pH <10.5) or by the presence of sufficient chloride ions (termed the corrosion threshold value), corrosion may occur. For corrosion to occur at a significant rate the following conditions are required: -

a reactive metal that will oxidise anodically to form soluble ions


-

a reducible metal that provides the cathodic reactant (typically hydroxyl ions)

dimension into the corrosion system, but are not considered here.

-

an electrolyte that allows ionic movement between the material and environment

The nature of steel corrosion in concrete depends on local conditions at the surface of the bar. High resistivity concrete with relatively deep covers tends to favour microcell corrosion where anode and cathode are close together and cause localized pitting. Conductive concrete contaminated with salt is often able to sustain more widely spaced anode and cathode sites, termed macro-cell corrosion.

It is important to note that the establishment of depassivating conditions at the steel (i.e. carbonation or chlorides) is not necessarily indicative of a high probability of corrosion damage since other factors (e.g. oxygen availability, moisture content) will largely determine the rate of corrosion. A schematic diagram of the corrosion process of steel in con crete is shown in Figure 1.

Corrosion Damage Once the passive layer on the reinforcing steel has been disrupted and corrosion is activated, the chemical reactions are similar whether the corrosion was initiated by chloride attack or by carbonation. Steel dissolves into solution and gives up electrons at the anode. Anodic reaction: Fe ↑Fe2++ 2e- . . . . . . . . . . . . . . . . . . . . . (1) The excess electrons are used up at the cathodic site where water and oxygen are reduced to hydroxyl ions.

Figure 1: Schematic of corrosion of steel in concrete

Four states of corrosion may be defined for reinforced concrete depending on environmental conditions1: -

Passive state where minute levels of corrosion are needed to sustain the ferric oxide film (typical of embedded reinforcement in sound, alkaline and uncontaminated concrete).

-

Pitting corrosion causing local breakdown of the passive film, usually due to the presence of chloride ions. Adjacent steel acts as the cathode, being considerably larger in area than the anode (typical of steel embedded in chloride contaminated concrete).

-

General corrosion due to an overall loss of passivity that results in multiple pits along the steel surface (typical of steel in carbonated concrete or concrete containing high chloride concentrations).

-

Active, low potential corrosion that occurs slowly when insufficient oxygen is available to sustain the passive film despite the high alkalinity of the concrete (typical of reinforcement embedded in concrete underwater).

Clearly only pitting and general corrosion represent a threat to the reinforcement and their severity will depend on a number of internal and external factors which need to be assessed when doing a corrosion survey. Internal factors include concrete microstructure, cover depth and moisture condition. External influences such as stray currents and microbial activity may introduce a new

Cathodic reaction: 2e- + H2O + ½O2 ↑2(OH)- . . . . . . . . (2) These two reactions are necessary for electrochemical corrosion to proceed. Little distress would be caused to the surrounding concrete however if steel merely dissolved into the pore water without further oxidation. Several more oxidation stages occur which form expansive corrosion products or rust capable of causing cracking and spalling of the surrounding concrete. The oxidation stages may be described as follows: Fe2+ + 2(OH)↑Fe(OH)2Ferrous hydroxide . . . . . . . . . . . . (3) 4Fe(OH)2 + O2 + 2H2O ................... . (4)

↑4Fe(OH)3 Ferric hydroxide . . .

2Fe(OH)3 ↑Fe2O3.H2O + 2H2O Hydrated ferric oxide . . ................... . (5) The expansion associated with rust is mostly due to hydrated oxides that may swell up to ten times the original volume of the steel. The type of corrosion product formed at the steel depends on environmental con ditions: -

red or brown rust forms under high oxygen concentrations, forming flakey rust which is relatively soft and easy to dislodge from the rebar

-

black rust forms under low oxygen concentrations, forming a relatively dense and hard layer that may be difficult to remove from the parent steel

Two major consequences of reinforcement corrosion are


125


commonly observed, cracking and spalling of the cover concrete as a result of expansion of the corrosion product, and a reduction of cross-sectional area of the rebar by pitting (usually only a problem in prestressed con crete structures). Manifestations of corrosion depend on a number of influences that include: -

geometry of the element (large diameter bars at low covers allow easy spalling)

-

cover depths (deep cover may prevent full oxidation of corrosion product)

-

moisture condition (conductive encourage well-defined macro-cells)

-

age of structure (rust stains progress to cracking and spalling)

-

rebar spacing (closely spaced bars in walls and slabs encourage delaminations)

-

crack distribution (cracks may provide low resistance paths to the reinforcement)

-

service stresses (corrosion may be accelerated in highly stressed zones)

electrolytes

The loss of serviceability of corroded reinforced concrete structures may be described by a three phase damage

through cracks in the cover concrete, resulting in spalling of concrete. Unfortunately most reinforced concrete structures that exhibit cracking and spalling have gone beyond the point where simple, cost-effective measures can be taken to restore durability. Condition surveys are therefore an important strategy to identify and quantify the state of corrosion of a structure timeously. Condition Surveys A detailed corrosion or condition survey is vital in order to identify the exact cause and extent of deterioration, before repair options are considered. Various diagnostic sheets are given in the Appendix for guidance during condition surveys. a) Visual assessment Corrosion damage may be identified and defined using a systematic visual survey. Classification of visual evidence of deterioration must be done objectively, following clear guidelines that define damage in terms of appearance, location and cause. Defects may be defined in terms of cracks (caused by corrosion, temperature, shrinkage or fatigue), joint deficiencies (joint spalls, upward movement, lateral movement, seal damage) surface damage (abrasion, rust stains, delaminations, popouts, spalls), changes in member shape (curling, deflection, settlement, deformation) and textural features (blow holes, honeycombing, sand pockets, segregation). Visual assessment of deterioration can provide useful information when done in a rational, systematic manner but the data may come too late for cost-effective repairs. Rebar corrosion damage is often only fully manifest at the surface after significant deterioration has occurred. Early evidence of distress can sometimes be detected by an experienced engineer before major distress takes place.

Figure 2: Three-phase corrosion damage model

b) Delamination survey

model shown in Figure 2 2.

A hammer survey or chain drag is a simple method of locating areas of delamination in concrete. Hollow sounding areas can be marked up on the concrete or recorded directly in a survey form. Delamination surveys often under-estimate the full extent of internal cracking and should not be considered as definitive. Radar and ultrasonic instruments may provide a more sophisticated approach to locating areas of delamination, particularly at greater depths.

The different phases are defined as follows: -

An initiation period, before corrosion is activated by either carbonation or chloride attack, during which negligible concrete deterioration occurs.

-

A propagation period in which active corrosion commences and cracking of the cover concrete occurs due to the formation of expansive corrosion products at the steel surface.

-

126

An acceleration period of damage where corrosion increases due to easy access of oxygen and water


c) Cover surveys Cover surveys are routinely done to locate the position and depth of reinforcement within a concrete structure.


Covermeters use an alternating magnetic field to locate steel and any other magnetic material in concrete (note that austenitic stainless steels are non-magnetic). Cover measurements may be unreliable when: -

rebar is at deep covers (e.g. covers greater than 80 mm)

-

measuring regions of closely spaced bars

-

measuring differing bar types and sizes (unless specifically calibrated) o other magnetic material is nearby (e.g. window frames, wire ties, bolts) To ensure reliable cover depths from a survey, direct measurements of rebar depths should be made by exposing a limited number of bars. Calibration can then be made for site specific conditions such as rebar type, concrete and environmental influences.

-

depth increments are chosen depending on the cover to steel and the likely level of chloride contamination (increments are typically between 5 and 25 mm)

-

dry powder samples are digested in concentrated nitric acid to release all chlorides

-

chlorides are analysed using a colorimetric or potentiometric titration

-

chloride contents are generally expressed as a percentage by mass of cement

-

chloride profiles may be drawn such that chloride concentrations may be interpolated or extrapolated for any depth (see Figure 3)

-

future chloride levels can be estimated from Fick's second law of diffusion

d) Chloride testing The presence of sufficient chloride at the surface of reinforcement is able to depassivate steel and allow corrosion to occur. Chlorides exist in concrete as both bound and free ions but only free chlorides directly affect corrosion. Measuring free chlorides accurately is extremely difficult and water-soluble chloride tests are unreliable, being strongly affected by the method of sample preparation. Further, bound chlorides may be released into solution under carbonating conditions or by dissolution, making all chlorides in concrete potentially corrosive. Chlorides are therefore most commonly determined as acid soluble or total chlorides in accordance with BS 1881 3. Chloride sampling and determination in concrete is illustrated in Figure 3 and is usually done in the following manner: -

concrete samples are extracted as either core or drilled powder samples

Figure 3: Chloride content determination and typical chloride profile

Chloride content by mass of cement (%)

Probability of corrosion

< 0.4 0.4 - 1.0 > 1.0

Low Moderate High

Table 1: Qualitative risk of corrosion based on chloride levels

The corrosion threshold depends on several factors including concrete quality, cover depth, and saturation level of the concrete. The probability of corrosion may be assessed from the following qualitative rating shown in Table 1 for acid-soluble chloride contents. Limitations of chloride testing of concrete are as follows: -

presence of chlorides in aggregates may give misleading results

-

chloride contents in cracks and defects cannot be accurately determined

Figure 4: Schematic of the carbonation process


127


-

slag concretes may be difficult to analyse with colorimetric titration methods

-

relatively large samples are required to allow for the presence of aggregates

e) Carbonation depth Carbonation depth is measured by spraying fresh concrete with a phenolphthalein indicator solution (1% by mass in ethanol/water solution). Phenolphthalein remains clear where concrete is carbonated but turns pink/purple where concrete is still strongly alkaline (pH > 9.0). Carbonation moves through concrete as a distinct front and reduces the natural alkalinity of concrete from a pH in excess of 12.5 to approximately 8.3, with a pH level of 10.5 being sufficiently low to depassivate steel. The progress of the carbonation front is shown in Figure 4. Environmental conditions most favourable for carbonation (i.e. 50 - 65 % R.H.) are usually too dry to allow rapid steel corrosion that normally requires humidity levels above 80% R.H. Structures exposed to fluctuations in moisture conditions of the cover concrete, such as may occur during rainy spells, are however vulnerable to carbonationinduced corrosion. Limitations to carbonation testing are as follows: -

phenolphthalein changes colour at pH 9.0 whereas steel depassivation occurs at a pH of approximately 10.5, hence the corrosion risk is slightly underestimated

-

some concretes are dark (e.g. slag concretes) and a distinct colour change is difficult to discern visually

-

phenophthalein may bleach at very high pH levels (e.g. after electrochemical realkalization)

-

testing must be done on freshly exposed concrete surfaces before atmospheric carbonation occurs

kinetics of the reaction. Rebar poten tials are normally determined in accordance with ASTM C876 using a copper/copper sulphate reference electrode connected to a handheld voltmeter 4. The qualitative risk of corrosion based on rebar potentials is shown in Table 2. Note that the technique is not recommended for car-bonationinduced corrosion where clearly defined anodic regions are absent. The procedure for undertaking a rebar potential survey is as follows: -

mark up a grid pattern in the area of measurement (not more than 500 mm centres)

-

make an electrical connection to clean steel by coring or breaking out concrete

-

check the steel is electrically continuous over the survey area using a multimeter

-

wet the concrete surface with tap water if the concrete appears to be dry

-

take and record readings either manually or using a data logger

-

check data on site to correlate with visual signs of corrosion

-

Rebar potential measurements are relatively quick to perform but have the following limitations:

-

interpretation of results must be done with caution (preferably by a specialist)

-

rebar potentials from carbonated concrete are difficult to interpret (the reading is a mixed potential of anodic and cathodic sites)

-

delaminations may disrupt the potential field producing false readings

-

environmental effects will influence potentials (e.g. temperature and humidity)

-

rebar potentials cannot be directly correlated with corrosion rates

-

stray currents may affect measured potentials

f) Rebar potentials Chloride-induced corrosion of steel is associated with anodic and cathodic areas along the rebar with consequent changes in electropoten tial of the steel. It is possible to measure these rebar potentials at different points and plot the results in the form of a 'potential map'. Measurement of rebar potentials may determine the thermodynamic risk of corrosion but cannot evaluate the Rebar potential (-mV Cu/CuSO4) Qualitative risk of corrosion < 200 200-350 >350 Table 2: Qualitative risk of chloride-induced corrosion

128

Low Uncertain High 4


Absolute values are often of lesser importance than differences in rebar potential measured on a structure. A shift of several hundred millivolts over a short distance of 300-500 mm often indicates a high risk of corrosion. g) Resistivity Concrete resistivity controls the rate at which steel corrodes in concrete once favourable conditions for corrosion exist. Resistivity is dependent on the moisture condition of the concrete, on the permeability and interconnectivity of the pore structure, and on the concentration of ionic species in the pore water of concrete

JBA Concerete Solutions


such that: -

poor quality, saturated concrete has low resistivity (e.g. less than 10 kOhm.cm)

-

high quality, dry concrete has high resistivity (e.g. greater than 25 kOhm.cm) Resistivity (kOhmcm)

Likely corrosion rate given corrosive conditions

< 12 12-20 >20

High Moderate Low

Table 3: Likely corrosion rate based on concrete resistivity

Measurement of resistivity is done with a simple in situ Wenner probe connected to a portable resistivity meter. The outer two probes send an alternating current through the concrete while the inner two probes measure the potential difference in the concrete. Once the concrete resistivity is known a rough assessment of likely corrosion rates can be made as shown in Table 3. This assessment assumes conditions are favourable for corrosion. Resistivity measurements are simple to perform on site but have several limitations: -

measurements are affected by carbonation and wetting fronts

-

surface conductive layers and rebar directly below the probe should be avoided

-

readings may be unstable in concretes with high contact resistance at the surface Corrosion rate (? A/cm2)

Qualitative assessment of corrosion rate

> 10 1.0 - 10 0.2 - 1.0 < 0.2

High Moderate Low Passive

are generally unreliable. Table 4 shows a qualitative guide for the assessment of corrosion rates of site structures 5. Epair Strategies Numerous repair options are available and new technologies continue to make an impact in the field of concrete repairs. The suitability and cost-effectiveness of repairs depends on the level of deterioration and specific conditions of the structure. a) Patch repairs Before patch repairs are considered it is important that the distinction between chloride- and carbonationinduced corrosion is appreciated. As a general rule chloride-induced corrosion is far more pernicious and difficult to treat than carbonation-induced corrosion. This often dictates a completely different approach to repairing damage due to the two types of corrosion. Carbonation-induced corrosion causes general corrosion with multiple pitting along the reinforcement. Carbonated concrete tends to have fairly high resistivity that discourages macro-cell formation and allows moderate corrosion rates. Steel exposed to corrosive conditions will therefore show signs of corrosion that can be easily identified (e.g. surface stains, cracking or spalling of concrete). Repairs are generally successful provided all of the corroded reinforcement is treated. Chloride-induced corrosion is characterized by pitting corrosion with distinct anode and cathode sites. The presence of high salt concentrations in the cover concrete means that macro-cell corrosion is possible with relatively large cathodic areas driving localized intense anodes. High corrosion rates can be sustained under such

Table 4: Qualitative assessment of site corrosion rates

h) Corrosion rate measurements Corrosion rate measurements are the only reliable method of measuring actual corrosion activity in reinforced concrete. A number of sophisticated corrosion monitoring systems are available, based primarily on linear polarization resistance (LPR) principles. These techniques require considerable expertise to operate reliably. Corrosion rate measurements on field structures are most commonly done using galvanostatic LPR techniques with a guard-ring type sensor to confine the area of steel under test. Experience indicates that corrosion rates fluctuate significantly in response to environmental and material influences and single readings

130


Figure 5: Formation of incipient anodes after patch repairs


conditions resulting in severe pitting of the reinforcement and damage of the surrounding con crete. Much of the reinforcement may be exposed to corrosive conditions without showing any signs of corrosion, this is particularly noticeable when corroded structures are demolished. Localized patch repairs of areas of corrosion damage are popular due to their low cost and temporary aesthetic relief. This form of repair has limited success against chloride-induced corrosion as the surrounding concrete may be chloride-contaminated and the reinforcement is therefore still susceptible to corrosion. The patched area of new repair material often causes the formation of incipient anodes adjacent to the repairs as shown in Figure 5. These new corrosion sites not only affect the structure but often also undermine the repair leading to accelerated patch failures in as little as two years. Consequently, it is necessary to remove all chloridecontaminated concrete from the vicinity of the reinforcement. Complete removal of chloride-contaminated concrete, where it is possible should successfully halt corrosion by restoring passivating conditions to the reinforcement. Mechanical removal of cover concrete is usually done with pneumatic hammer, hydrojetting or milling machines. This form of repair is most successful when treating areas of localized low cover, before significant chloride penetration has occurred. If repairs are only considered once corrosion damage is fairly widespread it will be expensive to mechanically remove chloridecontaminated concrete from depths well beyond the reinforcement.

cathode. In large concrete structures, corrosion control is theoretically unlikely due to the presence of oxygen already in the system. In practice barrier systems are generally ineffective due to the presence of defects in the new coating during application and further damage during service. Such an approach is more likely to promote the formation of differential aeration cells further exacerbating the potential for corrosion. The application of a hydrophobic coating (sometimes referred to as penetrant pore-liners) may be used to reduce the moisture content of concrete and thereby electrolytically stifle the corrosion reaction. The drying action works on the principle that surface capillaries become lined with a hydrophobic coating that repels water molecules during wetting but allows water vapour movement out of the concrete, to facilitate drying. Hydrophobic coatings using silanes and siloxanes are gen erally most effective on uncontaminated concrete, free from cracks and surface defects. The feasibility of such an approach is questionable for marine structures where high ambient humidity, capillary suction effects and presence of high salt concentrations all interfere with drying.

Patch repairs consist of the following activities that are briefly described below:-

removal of cracked and delaminated concrete to fully expose the corroded reinforcement

-

cleaning of corroded reinforcement and the application of a protective coating to the steel surface (e.g. anti-corrosion epoxy coating or zinc-rich primer coat)

-

application of repair mortar or micro-concrete to replace the damaged concrete

-

possible coating or sealant applied to the entire concrete surface to reduce moisture levels in the concrete

b) Coating systems A variety of coating and penetrant systems are available that are claimed to be beneficial in repairs of concrete structures. Barrier systems attempt to seal the surface thereby stifling corrosion by restricting oxygen flow to the

Figure 6: Sorptivity results from bridge cores

The long-term effectiveness of hydrophobic systems applied to new construction is not known but local studies suggest reasonable performance over 10-15 years service. The Storms River bridge was coated with a silane system in 1985 and concrete cores were extracted from several parts of the structure in 1996 for analysis 6. The effect of the hydrophobic coating on absorption was determined by sorptivity testing at increasing depth increments into the concrete. Sorptivity results are shown in Figure 6 for arch and column concrete. The sharp increase in sorptivity at depths between 0.5 and 3 mm may be ascribed to the


131


Likely inhibition

Corrosive conditions

Good

Mildly corrosive, low chlorides or carbonation

Moderate

Poor

Moderate levels of chloride at rebar (i.e. <1%)

Concrete conditions

Severity of corrosion

Dense concrete Limited corrosion with good cover with minor pitting depths (> 50 mm) of steel Moderate quality concrete, some cracking

High chloride levels Cracked, damaged concrete, low at rebar (i.e. > 1%) cover to rebar

Moderate corrosion with some pitting Entrenched corrosion with deep pitting

Table 5: Likely performance of migrating corrosion inhibitors in concrete

presence of the silane in the concrete near-surface zone. c) Migrating corrosion inhibitors A corrosion inhibitor is defined as a chemical substance that reduces the corrosion of metals without a reduction in the concentration of corrosive agents. Corrosion inhibitors work by reducing the rate of the anodic and/or cathodic reactions thereby suppressing the overall corrosion rate. The effectiveness of migrating corrosion inhibitors is generally controlled by environmental, material and structural factors, shown in Table 57. Migrating corrosion inhibitors are generally organic-based materials that move through unsaturated concrete by vapour diffusion. Organic corrosion inhibitors such as amino-alcohols are believed to suppress corrosion by primarily being adsorbed onto the steel surface thereby displacing corrosive ions such as chlorides. The adsorbed organic layer inhibits corrosion by interfering with anodic dissolution of iron while simultaneously disrupting the reduction of oxygen at the cathode. When assessing the suitability of repairs with migrating corrosion inhibitors, two important issues must first be considered: -

the likely penetration of the material into the concrete

needs to be determined -

the severity of the corrosive environment at the reinforcement must be quantified

Migrating corrosion inhibitors are designed to move fairly rapidly through partially saturated concretes that allow vapour diffusion. Penetration has however been found to be poor in near-saturated concretes typically found in partially submerged marine structures. This poor penetration performance may be ascribed to high moisture and salt levels that prevent significant vapour diffusion through the concrete. It is critical therefore that satisfactory penetration of corrosion inhibitors is checked before undertaking full-scale repairs. The performance of migrating corrosion inhibitors in controlling chloride-induced corrosion is largely dependent on chloride levels at the reinforcement. Work done by Rylands indicates that effective inhibition is not possible at chloride levels above 1.0% at the reinforcement 8. This can be seen in Figure 7 where ribbed steel bars embedded at 25 mm in a grade 40 portland cement concrete were subjected to wetting and drying cycles with a salt solution for a period of 18 months. Concrete blocks were either controls (CON) or contained organic corrosion inhibitor, either admixed during casting (ADM) or coated after 30 cycles (CTG). The chloride content at the level of the reinforcement was approaching 2% at the time of application of the migrating corrosion inhibitor and resulted in poor inhibition. Better inhibition is possible if treatment is done earlier when chloride contents are lower. The effectiveness of migrating corrosion inhibitors appears to be enhanced when used in combination with hydrophobic coatings to reduce moisture levels in concrete. This has been noted in both laboratory trials and field monitoring of repairs. Such an approach has also been found to be effective in the repair of carbonationinduced corrosion damage. d) Electrochemical techniques Corrosion of reinforcement in concrete is an electrochemical process that occurs when embedded steel is depassivated by a reduction in concrete alkalinity or the presence of corrosive ions such as chlorides. Two repair techniques, electrochemical chloride removal and realkalization, attempt to restore passivating conditions by the temporary application of a strong electric field to the cover concrete region.

Figure 7: Corrosion rate measurements with time for grade 40 concrete

132


Realkalization is the process of restoring the original alkalinity of carbonated concrete in a non-destructive manner. The electrochemical treatment consists of


placing an anode system and sodium carbonate electrolyte on the concrete surface and applying a high current density (typically 1 A/m2). The electrical field generates hydroxyl ions at the reinforcement and draws alkalis into the concrete. Alkaline conditions may be restored in the concrete in as little as one to two weeks using the system. Electrochemical chloride removal (ECR) is a more timeconsuming and complex technique and its suitability needs to be carefully assessed. Chloride removal is induced by applying a direct current between the reinforcement and an electrode that is placed temporarily onto the outside of the concrete. The impressed current creates an electric field in the concrete that causes negatively charged ions to migrate from the reinforcement to the external anode. The technique decreases the potential of the reinforcement, increases the hydroxyl ion concentration and decreases the chloride concentration around the steel thereby restoring passivating conditions. Figure 8 shows the basic principles of ECR. The effectiveness of ECR depends on several factors that include the following:-

extent of chloride contamination in concrete

-

structural configuration including depth and spacing of reinforcement

-

applied current density and time of application

-

pore solution conductivity and resistance of cover concrete

-

presence of cracks, delaminations and defects causing uneven chloride removal

Figure 9: Chloride profiles before and after ECR treatment for 8 weeks

forced deeper into the concrete during the process. There is a risk that chlorides left in the concrete may diffuse back to the reinforcement and cause further corrosion with time. The feasibility of using ECR depends on several factors such as:-

the presence of major cracking, delaminations and defects that will require repair before ECR

-

large variations in reinforcement cover that will cause differential chloride extraction and possible shortcircuiting

-

reactive aggregates requires special precautions to avoid possible alkali silica reaction; lithium salts should be used in these cases

-

prestressed concrete structures may be susceptible to hydrogen embrittlement after ECR; special precautions are needed to eliminate this risk

-

temporary power supplies of significant capacity are required during application of ECR

e) Cathodic protection systems

Figure 8: Schematic illustration of electrochemical chloride removal technique

ECR typically takes 4-12 weeks to run at current densities within the normal range of 1-2 A/m2. Results from ECR trials performed in the laboratory are shown in Figure 9 and indicate that complete extraction may take longer than 8 weeks at a current density of 1 A/m2 9. In some cir cumstances chlorides beyond the reinforcement may be

Cathodic protection systems (CP) have an excellent track record in corrosion control of steel and reinforced concrete structures. The principle of CP is that the electrical potential of the steel reinforcement is artificially decreased by providing an additional anode system at the concrete surface. An external current is required between anode and cathode that diminishes the corrosion rate along embedded reinforcement. The current may be produced either by a sacrificial anode system or using an impressed current from an external power source. Sacrificial anode systems consist of metals higher than steel in the electrochemical series (e.g. zinc). The external anode corrodes preferentially to the steel and supplies electrons to the cathodic steel surface. Sacrificial anode


133


systems are most effective in submerged structures where the concrete is wet and resistivity is low. Warm temperatures are also generally required for sacrificial CP systems (i.e. above 200C). CP systems more commonly use an external electrical

The first major CP repair of a reinforced concrete structure in South Africa was done at the Simonstown Jetty in 1996 10. The structure was almost 80 years old and in an extremely poor condition with widespread chloridecorrosion damage. Several previous patch repairs had failed and the concrete was contaminated with chlorides making conventional repairs unfeasible. An impressed current CP system was installed with metallic ribbon anodes protected within a sprayed concrete overlay. The structure has been restored to full serviceability and should require no further repairs for at least 40-50 years. f) Demolition/reconstruction

Figure 10: Typical cathodic protectipon layout

power source to supply electrons from anode to cathode. The anode is placed near the surface and is connected to the reinforcement through a transformer rectifier that supplies the impressed current (see Figure 10). Anodes may be conductive overlays, titanium mesh within a sprayed concrete overlay, discrete anodes or conductive paint systems. Anode systems are usually designed for a minimum service life of 20 years but may last in excess of 50 years. Before CP repairs are undertaken several factors need to be considered: -

reinforcement must be electrically continuous

-

concrete cover must be uniformly conductive and free of delaminations

-

alkali reactive aggregates and prestressing steel need special treatment

Deterioration of reinforced concrete structures is often so advanced that demolition and reconstruction becomes viable. This option should only be considered as a last resort since the total cost (capital costs plus loss of service and temporary works) is usually well in excess of repairs costs. Corrosion damage is also generally confined to near-surface regions and engineers often over-estimate the extent of damage to corrosion-dam-aged structures. Recent demolition of several bridge-decks along the Cape coast revealed that actual corrosion damage was less than anticipated. Demolition and reconstruction is often preferred by engineers who have limited repair experience or lack confidence in new repair systems. It is crucial nevertheless that lessons are learnt from the old structure when designing the replacement. Guidance about ensuring durable reinforced concrete structures is given in Monographs 1 and 2. Economics of Repairs Repairs of reinforced concrete structures damaged by corrosion have often proved to be unsuccessful with further damage occurring after repair. Reasons for the poor performance of repairs include:-

lack of understanding of deterioration processes

power must be available to drive the impressed current in the structure

-

inadequate investigation and testing prior to repairs

-

inadequate funds to undertake satisfactory repairs

CP repair of concrete structures requires a thorough corrosion survey by a specialist and the design needs to be undertaken by a corrosion expert. Reliable CP systems are fully controlled and monitored by a series of embedded sensors in order to ensure optimum performance. This is essential since under or overprotection of the reinforcement may be potentially harmful to the structure or the CP system. Continuous monitoring of CP systems is usually done remotely by modem and the power consumption during operation is extremely small.

-

ineffective or inappropriate repairs being specified

-

poor supervision and implementation of repairs on site

-

134


Repairs are not generally anticipated by owners and funds for repairs are nearly always extremely limited. Economics largely dictate the timing and scale of repairs but unfortunately only short-term costs are often considered. Whilst corrosion damage is to some degree unique to each structure some basic tenets hold for most cases. -

Performance of the concrete structure prior to

Unipave Engineering Products


treatment often dictates the likely performance after repair. Structures with high levels of damage and rapid rates of deterioration require more substantial repair than those less seriously affected. -

The timing of treatment is crucial since corrosion rates and damage increase with time. A structure that has been neglected and allowed to reach an advanced level of damage will not respond to 'quick-fix' solutions. Conversely a structure that is repaired early enough may be restored to full serviceability relatively cheaply.

-

The effectiveness of treatments in retarding corrosion is not equal and may range from highly effective to detrimental (e.g. cathodic protec tion versus patch repairs) Option

1

2

3

4

5

Original 60 MPa 30% 60 MPa 30% 60 MPa 30% 60 MPa 30% 60 MPa design fly ash 55 fly ash 30 fly ash 40 fly ash 40 100%PC 75 mm cover mm cover mm cover mm cover mm cover Repairs/ maintenance

None

Relative costs

1.0

Surface Patch repairs Cathodic Patch repairs treatment at after 20 and protection after 15, 25 10-year 35 years after 20 after and 35 years intervals 20 2.0

2.3

3.0

3.5

Table 6: Total life cycle costs of typical beam members exposed to marine environment Notes on repair options:Option 1. Durability design for maintenance free 40 year service life Option2. Based on anticipated life of surface treatment Options 3-5. Based on the likely stage at which spalling damage becomes excessive Option 5. Design required by SABS 0100:1992

Importantly, repairs costs need to be compared in a rational way by comparing life-cycle costs of the structure. Scott showed that when life-cycle costs are compared, a maintenance-free structural design is cheaper than cutting initial costs and deferring some money for repair and maintenance at a later date (data shown in Table 6) 11.

considered, a practical example is given in the Appendix. Closure The notion that reinforced concrete structures require no maintenance or repair during their service life is gradually being dispelled. It has been said that owners will have to pay for durability at some point in the life of a structure. Inadequate designs with excessive cost-cutting will merely transfer the savings in capital costs to much more expensive repairs at a later stage. While accountants may encourage some deferment of capital costs into maintenance, experience suggests that investments in the form of design and construction for durability bring better rewards than allowing for maintenance. Despite this evidence, economic imperatives that attempt to maximise short-term profits, often impact detrimentally on the durability and service life of infrastructural developments. Repair of reinforced concrete structures needs to be undertaken in a rational manner to guarantee success. An increasing number of repair options are available that must be considered in terms of cost, technical feasibility and reliability. Engineers need to understand all the relevant material, structural and environmental issues associated with concrete repairs in order to make intelligent choices. High quality repairs require a thorough investigation into the causes of deterioration, appropriate repair specifications and competent execution of the repair work. This can only be done when structural investigations are carried out by independent experts, specifications are drawn up by engineers with specialist repair expertise and repairs are undertaken by competent contractors. Appendix 1: Repair example

Strohmeier showed that repair costs escalate dramatically as deterioration proceeds and that repairs should be done as soon as distress is noted 12. This research helped quantify what many engineers had long realized; that durability-based designs are cost-effective in the longterm and that delays in repairs cause an exponential increase in costs.

A 60-year old bridge structure is in need of major repairs arising from widespread corrosion damage. The bridge spans a tidal estuary with direct exposure to seawater splash and spray action. Concrete is heavily contaminated with salt and chloride levels at the reinforcement are around 1.0% by mass of cement. Damage in the form of cracking, spalling and delaminations are widespread over much of the structure and are the result of chlorideinduced corrosion. Urgent repairs are essential to restore full serviceability to the bridge.

Engineers considering repair of concrete structures do not have the freedom to change either the original design or the timing of the repairs. Repairs therefore need to be considered on the merits, logistics, costs and risks of the many options that are available to rehabilitate the structure. To illustrate some of the issues that need to be

Rough estimates of service life of the various options are based on recent experience in South Africa and specialist publications13,14,15. Whilst the projected performance of the various repairs is a subjective assessment, the figures serve to illustrate the many issues that need to be considered when costing repairs.

136



For the purposes of costing the repair options, the following assumptions are made:-

unescalated 2001 costs are used due to uncertainties about future discount, inflation and tax rates

-

site establishment costs are fixed at R 250 000 for each repair option

-

total area of concrete under repair is 2000 m2

-

unit rates for repair include allowance for labour, materials, access and supervision

-

repairs are focused on chloride-induced corrosion damage only

A The following repair options are considered for the bridge. A Localized repairs of corrosion-damaged areas with only cosmetic con sequences. Assuming 15% of the structure requires patching and that concrete is only broken back to the reinforcement, a unit rate of R250/m2 is used. Given the limited nature of the repairs and the likelihood of incipient anode formation an effective life of 8 years is con sidered possible. B More extensive mechanical break-outs and patching are done with all corroded reinforcement being exposed, cleaned and a good quality repair material used for patching. Approximately 30% of the structure is treated at a unit rate of R280/m2. Despite the effort made to repair the structure, corrosive conditions still exist at the reinforcement and further corrosion damage limits the effective life to 12 years before more repairs must be considered. C Conventional corrosion repairs are done but a migrating corrosion inhibitor is applied to the repaired concrete surface together with a hydrophobic coating (silane/siloxane). Mechanical breakout is limited to damaged areas of concrete and not all corrosion on reinforcement is removed resulting in a unit rate of R300/m2 . This includes the cost of the migrating corrosion inhibitor and coating at R40/m2. The chloride level at the reinforcement (1.0%) is at the upper level for corrosion inhibitor performance resulting in an effective service life of only 15 years. D Electrochemical chloride extraction is applied to the concrete to remove chloride from around the steel. The cost of the system is approximately R750/m2 for a six week application and includes repair to damaged concrete. Unfortunately not all the chloride is removed from the concrete resulting in an effective service life of 25 years. E Cathodic protection is applied to the structure to protect the embedded reinforcement. The cost of the

system is R900/m 2 at installation and a nominal maintenance and monitoring fee of R5000 per year. The anode system is designed to last 50 years thereby dictating the effective life of the system. Present value costs for the various options are shown in Table A1. From these findings it is clear that initial repair costs and total repair costs over 40 years vary significantly. Timing Option A

Option B

Option C

Option D

Option E

Initial

0.75

0.81

0.85

1.75

2.05

20 years

2.25

2.43

1.70

1.75

2.15

40 years

3.75

3.24

2.49

3.50

2.25

Table A1: Total present value costs (million rands)

Item

Example Background data

Structure name

Identification, reference number

Location

Physical address or location

Environment

Severity and type of exposure

History

Age, design data, repairs

Date inspected

Date

Surface condition

Honeycombing, bleeding, voids, popouts

Early cracking

Plastic settlement or plastic shrinkage

Concrete quality

Surface hardness, density, voids, colour

Observation

Original condition

Rebar cover

Covermeter survey, mechanical breakout Structural Overloading, dynamic effects, structural cracking effects Present Condition Surface damage

Abrasion, chemical attack, spalling, leaching

Staining

Rebar corrosion, AAR gel, effloresence, salts

Cracking

Width, pattern, location, causes of cracking

Rebar Condition

Visual examination of bar, rust and pitting damage

Carbonation Indicator test on cores or mechanical breakouts Delamination

Size, frequency, severity of delamination

Previous repairs

Integrity of repairs, signs of damage near repair locations

APPENDIX 2: Diagnostic sheets Table A2: Checklist for investigation of structural deterioration

Option A is most cost-effective when only short-term costs are considered but most expensive in the longer-term. For a structure that only has to last another 20 years, option C may be preferable whereas for 40 years further service, option E is most economical for the hypothetical example.


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Type of corrosion

Environment or causative conditions

Significant features of deterioration

Chlorideinduced

Marine environments Industrial chemicals Admixed chlorides (older structures)

Rapid and severe corrosion Distinct anode & cathode regions Corrosion damage may affect structural integrity

Secondary forms

Artificially induced

Visual evidence / associated factors

Confirmatory testing

Reinforcement Rust stains, cracking along corrosion reinforcement, spalling of cover concrete, delamination of cover concrete

Cover depth of rebar Carbonation & chloride testing Exploratory coring Electrochemical testing

Alkali aggregate reaction

Expansive map cracking, restrained cracking following reinforcement, white silica gel at cracks

Core analysis for gel and rimming of aggregates Petrographic analysis Aggregate testing

Shrinkage/ creep

Characteristic cracking, Concrete core analysis excessive displacements, Loading and structural time dependent movements, analysis Aggregate and binder exposure to drying conditions analysis

Chemical attack

Surface attack, salt deposits on surface, expansive internal reactions causing cracking, exposure to aggressive waters

Chemical analysis of concrete Core examination for depth of attack and internal distress

Softwater attack

Primary cracking due to alkali Corrosion localized in regions aggregate reaction, delayed where cracks intersect rebar ettringite formation, structural Other forms of distress cracking evident in concrete (i.e. AAR gel deposits)

Surface leaching of concrete, exposed aggregate, exposure to moving waters in conduits

Chemical analysis of water Core examination for leaching damage

Fire damage

Bimetallic corrosion Partial Generally very localized sealing of concrete High intense corrosion due to well temperatures (>2000 C) Patch defined anode/cathode repairs of corrosion regions

Surface discolouration, concrete spalling, thermal cracking, buckling, loss of strength, microcracking

Core examination for colour variations, steel condition Petrographic analysis Specialist techniques

Structural overload

Major cracking in areas of high stress, localized crushing, excessive deformations and deflections

Loading and structural analysis Core testing for compressive strength and elastic modulus

Carbonation- Unsaturated concrete Polluted General corrosion along rebar induced environments Low cover depths Moderate corrosion rates to steel except when wet & dry faces are close Corrosion damage generally only affects aesthetics Stray current DC power supplies Railway General corrosion of rebar systems Heavy industries, exposed to moist conditions smelters Corrosion not confined to low cover depths Large crack widths possible Chemical induced

Type of deterioration

Corrosion generally High sulphate groundwaters Fertilizer factories Industrial associated with near saturated conditions Concrete plants Sewage treatment works deterioration occurring together with corrosion

Table A3: Conditions and features of different forms of reinforcement corrosion

Table A4: Diagnostic sheet for concrete deterioration (all forms)

References

-

Mackechnie, J.R., Alexander, M.G. and Rylands, T., 'Laboratory trials with an organic corrosion inhibitor', 14th Int. Corrosion Congress, Cape Town, 1999, CD-ROM.

-

Mackechnie, J.R. and Le Maire, H.R.A., 'Electrochemical extraction of chlorides from OPC and fly ash concrete', Concrete Beton, 82, 1996, pp 9-17.

-

Stevenson, C.E., Unpublished MSc thesis in progress, University of Cape Town, 2001.

-

Alexander, M.G. and Scott, A., 'Designing reinforced concrete structures for durability and economy in marine environments', SAICE Journal, 41(4), 1999, pp 15-21.

-

Strohmeier, J.H. and Alexander, M.G., 'Deterioration, repair and maintenance of reinforced concrete structures in the Cape Peninsula', Concrete Beton, 81, 1996, pp 14-21.

-

Mackechnie, J.R., 'Observations from case studies of marine concrete structures', SAICE Journal, 40(4), 1998, pp 29-32.

-

Addis, B.J. and Basson, J.J., 'Diagnosing and repairing the surface of reinforced concrete damaged by corrosion of reinforcement', Portland Cement Institute, Midrand, 1989.

-

Standards Australia, 'Guide to concrete repair and protection', ACRA, Homebush, 1996.

-

Arup, H., 'The mechanisms of the protection of steel by concrete', Corrosion of reinforcement in concrete construction, SCI, 1985.

-

Miyagawa, T., 'Durability design and repair of concrete structures: chloride corrosion of reinforcing and alkali aggregate reaction', Magazine of Concrete Research, 43(156), 1991, pp 155-170.

-

British Standards Institute, 'Chloride content determination for concrete', BS 1881 Part 124, 1988.

-

American Society for Testing and Materials, 'Standard test method for half-cell potential measurement of reinforcement in concrete', ASTM C876, Philadelphia, 1991.

-

Broomfield, J.P., 'Corrosion of steel in concrete: appraisal and repair', Chapman and Hall, 1997.

-

Hoppe, G.E. and Varkevisser, J., 'Long term monitoring of the effectiveness of the silane impregnation of a concrete arch bridge to inhibit further effects of alkali aggregate reaction', FIP Symposium: The Concrete Way to Development, CSSA, 1997, pp 777-786.

-

138

Mackechnie, J.R., Alexander, M.G. and Rylands, T., 'Performance of Ferrogard corrosion inhibitor in chloride environments', Unpublished report, University of Cape Town, 2000.


Speedcrafts Ltd

Concrete Repair & Rehabilitation

Repair and Rehabilitation of Corrosion Damaged Concrete Structures

P. Srinivasan Principal Scientist, ACTEL, CSIR- Structural Engineering Research Centre , CSIR Campus, Taramani

C

orrosion of steel reinforcement in concrete structures is a techno-economic problem for several reasons. Technically (i) it poses challenges in research and development to discover methods and materials either to control or prevent corrosion (ii) inspite of considerable research work world-wide, it is now well recognised that corrosion in plain carbon steel can only be controlled and a total prevention is nearly an impossible task (iii) corrosion of reinforcing steel in concrete is peculiar in the sense that the corrosion product, because of its volume growth, causes cracking to the concrete. This physical effect together with sectional loss of reinforcing bars affect the load carrying capacity, serviceability, and the service life of a structure (iv) rehabilitation of corrosion damaged structures is often cumbersome requiring high technical expertise and competence. This paper highlights the materials and techniques for the repair and rehabilitation of corrosion damaged concrete structures. Few case studies are also presented. Steel is passive under high alkalinity environment, and therefore corrosion will not occur. Then, there are two ways to initiate the onset of corrosion. One is by the penetration of carbon dioxide from the environment into the cover concrete and the other is the penetration of water containing dissolved salts through the concrete cover or through a concrete crack. In the first case, the alkalinity of the concrete surrounding the steel could be reduced by carbon dioxide which reacts with calcium hydroxide in cement paste to form calcium carbonate (called carbonation of concrete) and further to form carbonic acid with the pore solution. The reduction of calcium hydroxide leads to a low pH value. This creates an environment for the corrosion of steel to take place. In the case of chloride diffusion, the alkalinity of concrete is not reduced, but when the chloride ion concentration is high enough, reaching a certain ratio with the hydroxyl ions (Cl/OH), the

140


deapssivation of steel takes place and corrosion of steel may start. The required treatments for restoring the protective environment for steel depend on the extent and cause of the corrosion damage: Carbonation-induced corrosion damage. Under such conditions, carbonated concrete should be removed and new concrete should be installed, re-passivation is provided by the new repair mortar or concrete. Chloride-induced corrosion damage. Under such conditions, if chloride has penetrated to the level beyond the steel reinforcements, removal of chloride around steel bars does not guarantee re-passivation as chloride ions may diffuse back from the deeper part of the concrete to the new concrete cover. This is the so-called redistribution of chloride after the repair. In this case, the repaired concrete will become cathodic and the rebar will be the anode. The corrosion will occur in the bars immediately. Other factors may influence the re-passivation of steel, for instance, coating of the steel reinforcements, and the application of membranes or sealers to limit the moisture content. In most cases, the strategy of repair is either a comprehensive or a partial repair of the concrete member. These strategies are common in the rehabilitation of concrete and they depend on the structural system, external environmental factors, and the degree of structural degradation. Steps in executing repair There are several regular steps in the repair of all structures exposed to corrosion. -

The first step is to strengthen the structure by performing structural analysis and designing a suitable


location for the temporary support. -

The second step is to remove the cracked and delaminated concrete. It is important to clean the concrete surface and also the steel bars by removing rust. After rust is removed by brush or sand blasting, the steel bars should be painted with epoxy coaling or replaced; additional steel rods shall be added if necessary. Then new concrete can be poured.

-

The final step is to coat the concrete member with concrete surface coating as external protection. These steps will be explained in detail in the following sections.

Materials The materials adopted for repair of corrosion damaged structures are described below: Polymer Concrete Three to four fold increase in strength up to 140 N/sq mm has been obtained using polymer in concrete. Corresponding increase in tensile strength of concrete is also achieved by polymer impregnation. The durability of polymer impregnated concrete is substantially increased when exposed to freeze-thaw cycles. This has been the Ingredients

Materials Binder

Additive

strong reason for its application in cold regions, and against corrosive salts and acids. These properties can be fully utilised in repairs and renovation of old structures damaged due to heavy wear and tear and by corrosion due to marine atmosphere. The development of techniques for such applications is in progress. Materials (monomers and polymers) used for the impregnation are Styrene, Polypropeleyne, Methyl Methacrylate (MMA) and Poly Methyl Methacrylate (PMMA). Epoxy Grouts, Mortars and Coatings Epoxy resin is a product of Epichlorohydrin and Bisphenol with or without additives such as plasticisers and dilutants. To get a cured epoxy resin product, a hardener (usually an amine) is blended with the epoxy resin at ambient temperature. The resin mortar may be obtained by adding fillers, such as, coarse sand or calcined bauxite grit. They develop excellent strength and adhesive properties, and are resistant to many chemicals. They have good chemical and physical stability; they harden rapidly and resist water penetration. In all, they provide a toughness that couples durability with crack resistance. Latex Modified Concrete The third group of materials which can be used for repair Application Requirements

Admixture

Thickness Limitation in/cm

Installation Temperature 0F/0C

Curing

Portland cement

Water reducer Air-entr

Wet 7 days

Portland Cement Concrete Portland cement

Water reducer Air-entr

Wet 7 days

HRWR Air-entr

Wet 7 days

Latex SBR

Wet 3 days

Portland Cement Mortar

Portland cement Microsilica Modified Portland Cement Concrete Latex Modified Portland Cement Concrete

Portland cement

Polymer Modified Portland Cement Mortar with Non-sag Filler

Portland cement

Magnesium Phosphate Cement Concrete

MagnesiumPhosphate cement

Preplaced- Aggregate Concrete

Portland cement

Epoxy Mortar

Epoxy resin

Methylmethacrylate (MMA) Concrete

Acrylic resin

Shotcrete

Portland cement

Micro- silica

Non-Sag fillers

Acrylic latex

Sheet 45 min2 days Pozzolans

Fluidifier

Wet 7 days -4 hrs.- 2 days 1 hr.- 6 hr.

Pozzolans

Water reducer acceler latex

Wet 7 days

Table- 1 Repair and Overlay Materials


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Drying Coeff. of thermal Shrink - age Expansion

1 HR

Compressive Strength Elastic Modulus Permeability Freeze Thaw Non-Sag Exo1 Day 3 Day 28 Day psi/Mpa (ConResis- Tance Quality Therm crete=10)

Comments

Moderate

Equal to substrate

0

9

Good

Moderate

Low

Low

Equal to substrate

0

9

Good

NA

Low

Low

Equal to substrate

0

6

Good

Good

Low

Low

Compat w/substrate

5

Excellent

NA

Low

Moderate

Compat w/substrate

5

Excellent

Moderate

Equal to substrate

9

Excellent

Low

High

ACI 30 4R - 23

Very low

Equal to substrate

10

Good

NA

Low

ACI 503.4

Low

(1.5-5) *concr.

1

Excellent

Moderate

High

Moderate

(1.5-5) *concr.

1

Excellent

NA

High

Vapor may Cause Problems inConfined areas

Moderate

Equal to substrate

6

Good

NA

Low

0

0

Excellent Moderate

ACI 506 R - 90

Table- 1 ( Contd.,)

purposes are the latex or acrylic-modified mortars. These are conventional patching mixes to which is added a synthetic latex. These additives actually give a mortar greater internal strength. For this reason they are usually preferred where strength or heavy loading is an important factor, for example, on bridge decks or for factory floors subject to heavy wheel loads. Both compressive and tensile strength are improved, while flexibility of the patch, a major factor influencing its durability, is increased substantially. Resistance to alkalies and dilute acids is good; the concrete has low water absorption properties and freeze-thaw stability is improved over a conventional patch. Bond strength of the latex modified mortar is said to be greater than the shear strength of the old concrete. Table- 1 gives the summary of the repair and overlay materials with the properties. Structure Strengthening One of the most dangerous and important first steps necessary for the repair is selecting the temporary support, which depends on the following: -

evaluating the state of the whole structure

-

determining how to transfer loads in the building and its distribution

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-

determining the volume of repair that will be done

-

determining the type of concrete member that will be repaired

-

the repair process must be carried out by a structural engineer with a high degree of experience who has the capability to perform the structure

Removal of damaged concrete There are several ways to remove the part of the concrete that has cracks on its surface and shows the effects of steel corrosion. These methods of removing the delaminated concrete depend on the ability of the contractor, specifications, the cost of breaking, and the whole state of the structure. The selection of the breaker methods is based on the cause of corrosion; if it is due to carbonation or chlorides, then one must also consider whether cathodic protection will be performed in the future. In this situation, the breaking work would take place on the falling concrete cover; it would be cleaned and all the delaminated concrete and cracked concrete parts removed. Then, high-strength, nonshrinking mortar would be poured. If the corrosion in steel reinforcement is a result of chloride propagation into concrete, most specifications


recommend removing about 25 mm behind the steel and making sure that the concrete on the steel has no traces of chlorides after the repair process. The difference between good and bad repair procedures is shown in Fig. 1.

Performance rates are about 0.025-0.25 m3 per hour using hammers weighing 10-45 kg, respectively.

The difference in the procedure of breaking the delaminated concrete is due to the difference in the causes of corrosion. Therefore, a careful study to assess the state of the structure and the causes of corrosion is very important to get high quality after the repair process. The evaluation process is the same as illness diagnosis. It is necessary and important to remove concrete for a distance greater than the volume required for removal of defective concrete so that proper steel can be reached. This will be important later in the repair process. Several methods are commonly used for breaking and removing the defective concrete and these are explained next.

This method has been commonly used since it was introduced to the market in the 1970s. It relies on the existence of water at the work site and on the removal of a suitable depth of concrete in a large area. It removes fragmented concrete, cleans steel bars, and removes part of the concrete behind the steel bars, as shown in Fig. 2 The water jet is used manually by an experienced worker who has previously dealt with the hose, which is pushing water under high pressure Very high safety precautions need to be applied to the worker who uses it and the site around it.

Manual Method

This is used to remove concrete cover in the case of large, flat surfaces. The grinding machine is usually used after the water gun or the pneumatic hammer to obtain final concrete breakdown around and under the steel reinforcement. Therefore, one must take into account whether the thickness of the concrete cover is equal. The rate of removal of the concrete by this machine is very fast.

One of the simplest and easiest methods is to use a hammer and chisel to remove defective concrete. This is considered one of the most inexpensive ways, but it is too slow compared with mechanical methods. However, mechanical methods produce high noise and vibration, have special requirements, and need trained labor. Using the manual method makes it difficult to spare concrete behind the steel. Any worker can manually break the concrete, but it is necessary to choose workers who have done repair work before as they must be sensitive in breaking the concrete to avoid causing cracks to the adjacent concrete members.

Water Jet

Grinding Machine

Clean concrete surfaces and steel reinforcements This phase removes any remaining broken concrete with a process of cleaning. At the same time, the process of assessing the steel and cleaning up and removing corrosion takes place.

Pneumatic Hammer Methods

Concrete

These hammers work using compressed air; they weigh between 10 and 45 kg. If they are used on the roof or walls, their weight will be about 20 kg. They need an attached small power unit to do the job, but in large areas may require a separate, bigger air compressor. This machine requires proper training for the worker that uses it. The use of pneumatic hammers is more economical when a small, rather than large, area is to be removed.

The stage of preparing a surface by pouring the new concrete is one of the most important stages of the repair process. Before application of the primer coating, which provides the bond between the existing old concrete and the new concrete for repair, the concrete surface must be well prepared, and this takes place according to the materials used. The concrete surface must be clean and not contain any oils, broken concrete, soil, or lubricants. The surface must be cleaned completely through sand blasting, water, or manually using brushes. This stage is very important and very necessary, regardless of the type of material used to bond the new concrete with the old. Clean Steel Reinforcement Bars

Good Repair Fig.1

Wrong Repair

After removal of the concrete covers and cleaning the surface, the next step is to evaluate the steel reinforcement by measuring steel diameter. If the cross-sectional area of the steel bars is found to have a reduction equal to or more than 20%, additional reinforcing steel bars must be added. Before pouring new concrete, one must be sure that the


143


development length between the new bars and the old steel bars is enough, as shown in Fig. 3 It is usually preferable to link the steel by drilling new holes in the concrete and connecting the additional steel on concrete by putting the steel bars in the drilled hole filled with epoxy. However, in most cases the steel bars are completely corroded and need to be replaced.In the case of beams and slabs that need to add additional steel reinforcement bars, it is preferable to connect the steel bars with concrete by drilling new holes in the concrete and making the bond of the steel bars in the holes by using adhesive epoxies. For beam repairs, the additional steel bars are fixed in a column that supports this beam. In the case of slabs, the steel bars are fixed in the sides of the beam that is supporting the slab, as shown in Fig. 3

Fig. 5 Use of concrete collars for strengthening concrete compression member

Dry Pack

Fig. 2 Concrete Surface after removing with water jet

Dry pack is a mortar mixture with a very low water-cement ratio, applicable for small area of repair. It is normally placed by hand. Materials commonly used in drypack are Portland Cement, sand, and water. Other types of Portland cement can also be used. Pre-placed Aggregate Concrete This essentially involves first placing the coarse aggregate in the forms, and thereafter filling the voids by pumping in cement grout (sanded or unsanded). This has been found to be suitable on areas where accessibility is a problem. Joint Sealers

Fig. 3 Installing additional steel

The techniques for the replacement of the cover concrete/ damaged concrete are given below. Shortcrete or Gunite Shotcrete or Gunite is mortar or concrete conveyed through a pressure hose and applied pneumatically at high velocity onto a surface. This material has found wide applications in several major repair works as it can be applied on vertical, horizontal or overhead surfaces, with the area to be repaired being either reinforced or unreinforced. For the purpose of design, gunite may be considered as good quality concrete of grade M.20. Shotcrete mixed with steel fibres can also be used.

144


Joint sealers are very important in concrete structures as every concrete structure has joints (or cracks). Joint sealers should ensure the structural integrity and serviceability. In addition, they should serve as protection against ingress of harmful liquids, gases, or other undesirable substances which would impair the quality of concrete. Jacketing Jacketing is the process of fastening a durable material over concrete and filling the caving with a grout that provides needed performance characteristics. The materials used for jacket are metals, rubber, plastics, and concrete. This restores structural values, protects the reinforcement from exposure to the harmful elements and improves the appearance of the original concrete. Jacketing materials may also be secured to concrete by means of bolts, screws, nails, or adhesives; by bond with the existing concrete; or by gravity. The method of securing employed, will depend upon the exposure, the material

Robbins Tunneling & Trenchless Technology (I) Pvt. Ltd


used and the positioning of the jacketing material. Fibre glass reinforced plastics, ferrocement, and other hard materials such as polypropylene can be used for jacketing. A few examples of guniting, jacketing, and strengthening are schematically shown in Figs. 4-7 respectively.

Cathodic Protection As discussed, the corrosion of reinforcement in concrete is an electrochemical process. Cathodic protection is a technique by which the electrical potential of the steel is increased to a level at which corrosion can not take place. It is widely used for both steel and concrete offshore structures, while on land it has been used for the protection of pipelines and similar structures. It has been used on a limited scale, for concrete structures as discussed below. Two different methods are employed, an impressed current and the use of sacrificial anodes. In the first the structure is connected to the negative terminal of a DC power source, ideally using an anode which does not corrode. In the second the reinforcement is connected to anodes with a more negative corrosion potential than steel, such as zinc or aluminium. The current is reversed and corrosion now takes place at the anode, which is gradually used up. In both cases, electrical continuity of the reinforcement is required. Fig. 8 shows the schematic setup for the cathodic protection.

Fig. 6 Beam strengthening with steel plates

Use of FRP Wrapping The growing interest in FRP systems for strengthening and retrofitting can be attributed to many factors. Although the fibers and resins used in such systems are relatively expensive compared with traditional strengthening materials like concrete and steel, labor and equipment costs to install FRP systems are often lower. Fiberreinforced polymer systems can also be used in areas with limited access, where traditional techniques would be very impractical-for example, a slab shielded by pipe and conduit. These systems can have lower life-cycle costs than conventional strengthening techniques because the FRP system is less prone to corrosion. Fiber-reinforced polymer (FRP) can serve as an alternative to the use of steel sheets. The use of FRP has a wide range of advantages and offers an alternative to the steel used in the strengthening process. There are different types of FRPs; the famous type is carbon fiber-reinforced polymer (CFRP), which is most commonly used as appropriate in practical applications and because of its unique properties in terms of resistance and the resistance with time, as well as resistance to stress.

Fig. 7 Replacement of concrete using pressurized forms

Corrosion Inhibitors Other Methods Other techniques employed on repair of corroded concrete structures include removal of chloride ions, cathodic protection, use of Fibre reinforced Polymer Wraps, corrosion inhibitors and concrete coatings. The details are given below

148


It has been shown that certain admixtures can be used to inhibit corrosion of the reinforcement in the presence of chlorides8. One that shows promise is calcium nitrite. When corrosion takes place in untreated concrete, the ferrous ions at the anode pass into solution and, in a secondary reaction, are converted to rust. With the calcium nitrite,


Fig. 8 Schematic diagram of CP including modern link and remote monitoring

ferric ions are formed which are insoluble and hence stay on the surface of the reinforcement, preventing further corrosion. The addition of calcium nitrite extends the time to corrosion initiation The corrosion rate, once corrosion is initiated, is less with calcium nitrite. Corrosion inhibitors can be classified based on their action and their chemistry and function: By their action:

Anodic inhibitors Cathodic inhibitors Ambiodic inhibitors

Suppressing the anodic corrosion reaction Suppressing the cathodic reaction Suppressing both anodes and cathodes

By their chemistry and function:

Inorganic inhibitors Organic inhibitors Vapour phase or volatile inhibitors

nitrites, phosphates and other inorganic chemicals amines and other organic chemicals a subgroup of the organic inhibitors (generally Amino alcohols) that have a high vapour pressure

Different types of coatings are available such as chlorinated rubber coating, vinyl coatings, epoxy coatings, acrylic based, polyurethane, etc. Sealers are an intermediate application between penetrants and coatings. They protect concrete by blocking the pores. Sealers are more viscous than penetrants and generally form a thin film on the surface of concrete.The effectiveness of surface treatment materials in preventing the ingress of aggressive ions depends on the penetrability of the material to provide protection of the concrete matrix. Various organic polymers are used as sealers and coatings. The most widely used penetrating materials tend to be siliceous, which line the pores of concrete forming silicone resins and thus provide protection through water repellent properties. Silane/siloxane primer with aliphatic- acrylic top coat gives good protection. CECRI also have developed and implemented concrete coatings. Case-studies Many corrosion-affected structures were investigated by the author at SERC for the its condition assessment through NDT & PDT and repair measures were formulated to increase its service life. One of the structure is the prill tower for the manufacture of urea and the age more than 30 years ( Fig.9) The structure is a RCC shaft and the thickness is 230 mm. Since the structure was constructed in marine environment, a coating was provided on the surface right from its construction. After the detailed investigation it was found that the carbonation depth was only 12 mm and chloride content in the concrete was within allowable limits. The reinforcements are found to be in very good condition. The test results have proved the efficiency of concrete coating. The other structure is a 30 year old RCC water tank constructed in Bangalore (Fig. 10) and was affected by

Coating to Concrete Surface treatment materials are often used to protect concrete from deterioration due to reinforcement corrosion. These materials are classified as Penetrants, Coatings, and Sealers. Penetrants are low viscosity liquids designed to penetrate into concrete and line its pores. They protect concrete by forming a hydrophobic layer and thus repel moisture, but they facilitate the evaporation of water vapor and other gases from the interior of the concrete mass. Coatings provide protection to concrete by forming a thick, protective film on the surface. However, due to minimal breathability, these materials may contribute to concrete deterioration.

Fig. 9 Prill Tower ( RCC Shaft- 30 Years Old)

Fig. 10 Water Tank repaired and coated with Concrete coating


149


environment : A comparison of carbon steel and SS bars", The Indian Concrete Journal, July 2001, pp 452-456.

corrosion. After detailed investigation, remedial measures were formulated. The repair measures consist of strengthening and finally a concrete surface coating was provided. It was found that after seven years of exposure, the carbonation depth was almost nil.

-

John L. Clarke (Editor),(1993), "Alternative Materials for the Reinforcement and Prestressing of Concrete", Blackie Academic & Professional, First edition,

Conclusions

-

Jones et al., (1995), "Concrete surface treatment : Effect of exposure temperature on chloride diffusion resistance", American Concrete Institute, Materials Journal, pp.197-208.

-

Srinivasan,P., Firdows M.Z.M., Prabakar J., and Chellappan, A., A simple accelerated test method for rapid assessment of chloride penetration of concrete with and without surface coating, The Indian Concrete Journal, January 2007, pp 43-47.

-

Srinivasan, P., Mohd. Firdows, M.Z., & Mani, K., "Surface coatings for protection of concrete in marine environment - performance evaluation through laboratory experiments", National Seminar on Harbour Structures, (NASHAR- 2003), IIT Madras, Chennai, 2122, February 2003, pp 341-350

-

Alonso, C. and Andrade C. (1990), "Effect of nitrate as a corrosion inhibitor in contaminated and chloride - free carbonated mortars", American concrete Institute, Materials Journal, pp.130-137.

Since corrosion is a complicated problem, the cause has to be diagnosed and proper material and technique has to be adopted. The cost of repair will vary with the type of technique being adopted. Repairing of a corroded damaged structure requires skilled personnel. The repaired structure has to be monitored periodically for their performance. References -

Page C.L, Treadway, KWJ and Bamforth PB (Editors) - Corrosion of reinforcement in concrete; Society of Chemical Industry; Elsevier Applied Science, May 1990.

-

IS 13620 -1993, "Specification for fusion bonded epoxy coated reinforcing bars".

-

-

British Standards institution, BS6744: 1986, "Austenitic Stainless Steel Bars for the Reinforcement of Concrete".

John Broomfield, (1999) "Corrosion inhibitors for steel in concrete", pp.45-47.

-

-

British Standards institution, BSEN-10088-1:1995, "Stainless Steels, Part 1 - List of Stainless Steels".

Berkeley, K.G.C. and S. Pathmanabhan, "Cathodic Protection of reinforcement steel in concrete", Bulter works, London.

-

-

Mani, K., and Srinivasan, P., "Service life of structures in corrosive

Mohamed A. El-Reedy, "Assessment and Repair of Corrosion",CRC Press, London, New York, 2007

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Nina Concrete Systems Pvt.Ltd


Comprehensive Guidelines for Execution of Epoxy/PU Floorings - Part II Step II: Installation procedures: Once it has been established that the base floor is capable of receiving epoxy/PU topping (outcome of step I ), installation sequence is to be set in motion. Installation procedure is broadly classified into three important steps: Prachi Mahajan Director, Neocrete Technologies Pvt Ltd

I

n part I of this article (which appeared in Jan issue), we dealt with the pre-installation guidelines and in this part II, we will address the following two important steps: -

152

installation procedures post-installation practices

-

Surface preparation Application of primer and underlay Application of topping

Let us discuss the above three steps in detail: Surface Preparation: This is the single most important step that determines the life of the flooring. Any slack in this step will adversely affect the quality and


durability of the flooring. Some of the questions that need to be answered before commencing the surface preparation are the following: What is the basic surface on which epoxy/PU topping needs to be applied? -

Vacuum de-watered concrete (power-trowelled) Manually trowelled PCC Cotta stone/Shabbat stone/ Granite /Kadappa/Marble Ceramic tile/vitrified tile

What is the status of the base floor? -

Clean or oil-soaked Existence of cracks, powdery surface etc


-

Soundness of the base floor and porosity etc

What is the thickness of the topping proposed as the surface profile to be created is directly proportional to the thickness of the coating? The answers to the above questions will lead you to the following decisions: Proper equipment to be used -

Floor grinding equipment Scarifier Shot-blasting equipment

Extent of surface profile required The following graph can be taken as a guideline to decide on both of the above questions:

Typical epoxy self-leveling floorings

The purpose of the surface preparation is to: -

-

-

Create a surface profile so as to create a mechanical key which increases adhesion strength Create a clean and dry base and remove loose particles Improve penetration of primer Removal of oil, grease and other contaminants that will impede bonding Remember the word “DCS”; Dry, Clean and Sound surface

Priming: After the surface preparation, the second step is to ensure that the surface is primed properly. The application of priming is as important as that of surface preparation in ensuring the longevity of flooring and most likely ignored by most of the contractors. As you are aware, concrete consists of micro-pores that typically do not allow penetration of fileer-rich epoxy coatings. Hence, it is essential that the initial

bonding is achieved by an epoxy primer that contains only resin and hardener and is of such viscosity so as to penetrate the pores of concrete thus creating a bond equivalent to that of spiked shoe on a soft floor. Thus, the concrete pores that are opened up by surface preparation get filled by a proper epoxy primer and increases the durability of the topping multi-fold. Depending on the porosity of the concrete, viscosity of the primer shall be properly chosen. Normally available epoxy primers will not adhere with vitrified tiles, polished marble/granite etc, which calls for specially formulated primers. Once the primer layer is cured which typically can take 4 to 12 hrs depending on temperature and humidity, screed underlay has to be applied. It is strongly advised that screed underlay is applied over primer not later than 24 hrs. Once the primer layer is hardened, the inter-phase bond between screed and primer can diminish. In case of delay in screed application, it is advisable to wipe the

primed surface with solvent like Xylene, MIBK etc. When the total thickness of floor topping exceeds 3mm, it is preferable to do a 2mm self-leveling screed underlay followed by 1mm self-leveling topping instead of 3mm topping together. Though this concept is being questioned by many, the argument in favour of doing a screed underlay has the following merits: -

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The function of screed underlay is to be provide a strong base with excellent compressive strength and bond-strength, while the function of topping is to provide abrasion resistance, chemical resistance, aesthetics etc. Thus it is prudent to formulate two different products to optimize the properties Leveling of undulated floors is much easier In essence, it can also reduce the overall price of the system

Topping: Execution of topping is very similar


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Typical epoxy self-leveling floorings

to that of execution of self-leveling underlay except the fact that topping contains a forth component i.e pigment. Pigment needs to be added to Component A (resin part), mixed well and component B & C are to be added sequentially. Proper mixing machines need to be used to ensure homogeneity of the system and consequent development of desired properties. Do not allow mechanical movement for 48 hours and chemical exposure for 7 days. Post-installation practices Some Do's and Don'ts -

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Clean the floor regularly with a mop at least once a day. Do not allow loose sharp particles to

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be strewn on the floor and ensure to remove the same immediately. Check the wheels of the vehicles regularly to ensure that there are no sharp particles adhering on the wheels. Rectify the leaking pipes and joints immediately. (eg. Oil carrying pipes in machines) Avoid dropping of tools and tackles on the floor Avoid dragging heavy loads like machinery, wooden crates etc Periodically inspect the areas and rectify damaged areas immediately. Do not clean epoxy floors with acid

Conclusion: Epoxy / PU floorings have been found to give an excellent service in


various industries such as pharmaceuticals, food, automobile/autoancillaries, textile, electronic and electrical industries, light engineering, chemical industries etc. However, it is important to ensure that the execution and maintenance have been done as per various standard procedures and I hope that this article helps in an indepth understanding of the same.

For further details: Neocrete Technologies Pvt Ltd

13-A, Satellite Tower, Film City road Goregaon (East), Mumbai - 400 063. Ph: +91-22-32937981, E-mail: [email protected] Web: www.neocrete.co.in www.neocrete.in

Sika India Pvt.Ltd

Quake Resistant Infrastructure

Unraveling the Secrets of 'Tokyo Sky Tree' Bhavani Balakrishna

T

okyo's new landmark, the Tokyo Sky Tree, towering at 634 meters, is the tallest free-standing structure in the world and the second tallest building after the Burj Khalif in Dubai which is 839 meters tall. The tower is located in Narihirabashi / Oshiage area, of the Sumida district in the capital city Tokyo. The high-rise tower will become a hub for terrestrial digital TV and radio broadcasting and also as an observation tower.

Picture Source: www.nikken.jp

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Unveiled just a few days ago, the Tokyo Sky Tower which mainly acts as a television transmitter was conceived when the city's old Sky Tower transmitter built in 1958 at just over 333 meters , had trouble broadcasting over the city's growing skyline, causing problems for digital television signals. The planning of the structure began in February 2005 when Tobu Railway Corporation expressed its desire to build a tower to both broadcasting services and administrative authorities of SumidaWard. The construction of the tower started in 2008 and was scheduled to be completed in Dec 2011. There was a two month delay due to the tsunami that struck Japan's coast last March. The construction site is at the center of a triangular plane surrounded by the three axes, the Sumida River and Arakawa River, and, to the south, railway lines running in an east-west direction and trunk roads. Perpendicular to each axis, various streets converge toward the focal point at which the tower stands. So, the tower has been designed to have three gates, each inviting people coming down through these streets. About 100 architects, planners and engineers were involved in the Tokyo Sky Tree design. Designer firm, Nikken Seikkei, has used concepts from traditional Japanese architecture principles - convex (Mukuri) and concave (Sori) curves for the design Tripod truss

of the Sky Tree. The tower has a triangular pyramid shape base. The triangular footprint turns into a cylindrical shape along the height. The gradual concave curvature of the ridge line of the triangle is called warp. Transition of this section to circular form through convex upward curvature is called camber. Camber structure is commonly used in columns of Heian and Nara era temples architecture. The curves also reflect the blade of a samurai sword and other traditional Japanese architectural shapes. The silhouette of the tower differs when it is seen from different angles. The observatories have a round shape to offer panoramic views of the river and the city. The first observatory is located at 350 meters above the ground. It will accommodate a restaurant, café and shops. The second observation deck and air corridor are at a height of 450 meters. The tower rises on three legs from an equilateral triangular footprint of side 68m. Triangular shapes reduce the structural steel required for construction. Lines from three apexes of the triangles converge about 50m above grade along the 600m height. The length to width ratio is about 9:1. In order to ensure that the structure could withstand the severest of earthquakes, it was essential to study the wind conditions at 600 meters above ground. A radiosonde balloon was flown Mid-tower framing

Lateral joint truss

Reflected view: Ring floor

Ribbed truss Ring truss Reflected view: Lateral joint floor

Tripod truss Outer tower framing Mid-tower framing Inner tower framing Core framing Ribbed truss Lateral joint truss Ring truss

Ribbed truss Tripod truss

Ring truss


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Tokyo Sky Tree Under Construction

to gather data related to the distribution of wind velocity levels and disturbance conditions at such altitude. Apart from the conventional subsoil investigation, in order to simulate soil behavior and determine the swaying of the tower during an earthquake, a micro-motion array observation was conducted to understand the soil formation at a depth of 3 kilometers from the ground surface. Since foundations of soaring towers like the Sky Tree are subject to large pulling-out force and push-down force, the Sky Tree foundation piles were built

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in the shape of nodular walls with the aim to resemble the function of “pins of spiked shoes” increase the friction resistance. The radial interconnection is expected to make the piles, the monolithically integrated into the ground. The steel tubes used at the base of tower are 10 centimeters thick with a diameter of 2.3 meters The Sky Tree tower uses highstrength steel tubes that are two times stronger than a standard steel channel. The entire tower structure is made up of truss elements: - Tripod truss - A built up column

Indigo Multitrade Pvt.Ltd


Added mass (balancing weight) swaying to the right

Added mass (balancing weight) swaying to the left

The swaying motions are counterbalanced throughout the entire structure

The swaying motions are counterbalanced throughout the entire structure The structural frames swaying to the left

The structural frames swaying to the right

Concept of Added Mass Mechanism

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composed of four steel columns, lateral steel members and braces. It is positioned at the top of a triangular plane and is one of the major frames to resist lateral force Lateral joint truss - Column section joining the mid-tower framing and ring trusses at every two courses

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(25m high). These act as loadcarrying members of lateral force (in-plane) and as stiffeners to resist buckling of tripod trusses and peripheral columns. Ring truss - Lateral members positioned at every course (12.5m). This truss acts as a stiffener to resist buckling of peripheral columns

To control vibrations, the designers have drawn inspiration from the traditional five-story pagoda temples in Japan that have never succumbed to earthquakes due to the temple's "Shimbashira” (Center Column) built at the center of the temple. In the case of the Sky Tree tower, it refers to the cylindrical shell built at its center (made of reinforced concrete and used as a staircase). The designers have named the present vibration-controlling system as "Shimbashira-Seishin (Center Column Vibration Control). The designers have also applied the concept of “Added Mass Control Mechanism “to ensure safety from swaying of the tower during an earthquake or string winds. The Added Mass Control Mechanism is supposed to reduce the response shear force by 40% during an earthquake. This mechanism involves controlling the swaying motions of a structure as a whole during an earthquake by providing added mass (balancing weight) so as to move in slightly delayed timing from the swaying motion in a counterbalancing way to set off the movement of the structure by the movement of the weight. Usually, steel ingots or concrete mass is used as the added mass, and sometimes

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At a height of 375m

Core column Flexible region: the core column and steel tower framing are connected with an oil damper.

At a height of 125 m Rigid region: the core column and tower framing are fixed with steel members.

Oil damper

Core column: reinforced concrete shell Sectional plan of the core column arrangement in the flexible region

equipment for building service systems, or a heat accumulator, are used for the same purpose. The present case of the core column (the staircase) used as the added mass is a world's first attempt. Picture Source www.nikken.jp, www.en.wikipedia.org www.savingjapan.net

Maini Construction Equipment Pvt.Ltd

Formwork Industry Analysis

Formwork Equipment:

Policy Initiatives Hold the Key for Continued Growth of Formwork Industry M.K. M.K. Prabhakar, Prabhakar, Associate Associate Editor Editor

I

f there is one segment among various types of construction equipment, which has been maintaining a steady pace of growth, without hitting frequent crests and troughs, it has to be that of formwork and scaffolding equipment. Steady, rather than spectacular growth has been the story of the formwork industry in India so far. With the construction industry growing at a CAGR of about 14 percent in the recent past, before the economic slowdown impacted it, the growth story of the formwork industry in the country makes for fascinating reading. It is a story that began in the 1990s when aluminum

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and steel based formwork and scaffolding systems began making an increasing appearance on the horizon. While there was growth, it was dominated by the unorganized sector. However, the last decade has seen, aided by the entry of several leading global players, the organized sector, which still only constitutes about 10 percent of the industry, gradually leading to improvement in quality standards and enabling customers a wider choice of formwork and scaffolding equipment. The Indian formwork industry is entering perhaps its most crucial phase this year. The government's policy


initiatives, vis-à-vis the envisaged US$ 1 trillion investment in infrastructure development during the 12th Five Year Plan period (2012-17), holds the key to the growth of the formwork industry. The Union Finance Minister is also expected to push for further reforms in the realty sector during the Union Budget 2012-13, which again holds the key to how fast the formwork industry grows. The industry though, is currently estimated to be growing at a rate of 1015 percent. While the growth may have been steady rather than spectacular, experts however agree that it is nevertheless evolving all the time. Today


has also been instrumental in pushing the demand for formwork. With a majority of infrastructure projects being implemented on a PPP mode, it has become imperative for project owners and investors to complete projects on time in order to generate revenues. By opting for system/engineered formwork contractors have realized that substantial savings are ensured, resulting in turn in faster return on investments.

“Interestingly, somehow this slowdown has increased the proportion of the usage of system formwork compared to traditional formwork in order to reduce the interest during construction time and several other factors“

Impact of Slowdown The country's economy grew last quarter at its slowest pace in more than two years, after maintaining an aggressive growth trajectory. Factors such as increased lending rates by the Reserve Bank of India (RBI) and the Euro Zone crisis have contributed to the economic slowdown. According to Mr.Anupam Sharma, CEO, Doka India, consequently the construction industry faced a slump and many sectors such as housing, power, high-rise, and infrastructure are witnessing a sluggish growth rate. However, Mr. Sharma observes that, “Interestingly, somehow this slowdown has increased the proportion of the usage of system formwork compared to traditional formwork in order to reduce the interest during construction time and several other factors. “ Continuing further he said that Doka India had last year launched “FramiXlife”, which is a panel

Anupam Sharma CEO, Doka India Pvt. Ltd.

formwork system, easy to handle and with a higher number of repetitions, to which the company has received tremendous response due to a variety of factors, including, scarcity of skilled manpower, reduced cycle time, safety and also because it is an economic option. Giving his take on the slowdown, Mr.Bharat Patel, Head-Sales & Marketing, Nav Nirman Beam Technics, remarked, “Forecasting of demand has now become difficult. Generally speaking, formwork suppliers are coming out with different product solutions to beat the slowdown.” Some in the

Picture Courtesy: www.doca.com

a typical customer in India, apart from looking at the technical attributes of products, also expects value added services, something that global players in the fray have realized. Two key factors have been driving forward the growth momentum of the formwork and scaffolding market. These include acute shortage of labour and rising construction costs, quite often due to project delays. Contractors are now looking towards automated formwork systems to address these two issues. The increase in the size of the projects, especially with respect to infrastructure and high-rise projects

Infrastructure development push holds key to formwork industry's growth


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The rapidly evolving Indian customer has realized that formwork systems are important for safer, faster and sustainable construction

industry however feel that the economic slowdown has had negligible impact. Giving his views on the subject, Mr.Ajay Maini, Director, Maini Construction Equipments (P) Ltd, another leading name in the field, when quizzed about the impact of the slowdown said, “ Not really, because of our versatile range of products in steel as well as aluminum formwork. MCE's aluminum formwork was launched when the entire industry was going through a rough phase, however, we were able to sustain and managed a steady growth.” Sharing similar views, Mr.Eldo Varghese, General Manager, Paschal Formwork (India) Pvt Ltd, when asked about the impact of the slowdown on the company's order book, said,” While the economic slowdown has slightly

“Forecasting of demand has now become difficult. Generally speaking, formwork suppliers are coming out with different product solutions to beat the slowdown”

Bharat Patel Head- Sales & Marketing, Nav Nirman Beam Technics

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Continued spurt in high-rise projects bodes well for the formwork industry

effected growth, but not to an extent that it could hit our order book. We could grow forward in the construction industry by rapid technological advancements and we are expecting good progress, year on year.” Industry experts however believe that in order to fully achieve the potential of system formwork, India needs to provide a boost to the infrastructure sector. There is unanimous opinion that a positive environment needs to be created for the construction industry and immediate steps such as curbing lending rates, which would in turn lead to a boost to power projects and the realty sector should be taken. Unique Paradox The story of the formwork and scaffolding industry in India is also interesting because of another reason. While the construction industry has been maintaining a robust pace of growth from the turn of 2000, the growth rate of the formwork industry has not kept pace. According to Mr.Anupam Sharma, due to lack of government regulations , most developers are not pressurized for safety, quality and time bound construction, which in turn allows them to use cheaper solutions. Adds Mr. Sharma, “Moreover, the knowledge of system formwork is not widespread, and hence clients are not aware of the advantages. While the initial investment in these systems may be higher, but if you consider the number of reuses, it actually works out


to be a cost effective blend with the advantages of being, safer, efficient and quality system.” These views are seconded by most of the industry analysts who feel that factors such as fast and timely construction of projects, lesser dependency on manpower, and the concern for increased quality and safety have driven all construction agencies to use modern System Formwork for critical projects. According to Mr.Eldo Varghese the government is making several efforts such as bring down the lending rates and giving boost to power projects in order to give fillip to growth of infrastructure projects. Some of the factors pointed by Mr.Varghese which would be driving forward the market in the near future include, need for speedy and quality construction, labour scarcity and safety requirement at sites. One key sector which could give further boost to the formwork market is power. With the situation on coal linkages and funding expected to improve in the second and third quarters of this fiscal, this sector could be just the trigger that the formwork industry has been waiting for in recent times. Thermal, hydro and nuclear power projects constitute more than 85 percent of the power sector. These apart there are other structure that the sector needs such as dams, power houses, water carrying tunnels , channels, containment tanks, TG deck, and cooling towers, etc, all of which need the use of system formwork for faster and safer construction.

Technocraft Group


“Not really (impacted sales), because of our versatile range of products in steel as well as aluminum formwork. MCE's aluminum formwork was launched when the entire industry was going through a rough phase, however, we were able to sustain and managed a steady growth”

from provisions for auxiliary systems like placing booms, while also offering adaptability to complex wall geometries are one of the reasons behind the spurt in high-rise projects throughout the country, a trend that is expected to continue in the near future. It is not surprising that every major player in the field such as Peri, Doka, Meva, Ulma, Pascahal, Navnirman, Technocraft, Maini, EPIC Indigo, to mention only some, offer specific products aimed at this fast growing market segment. Onus on Government

Ajay Maini Director, Maini Construction Equipments (P) Ltd

Vertical Growth Another key area which has been instrumental in aiding the growth of the formwork industry has that been of high-rise projects. While getting clearance for such projects remains an area of concern, there is no doubting the fact that vertical growth is here to stay in India and therefore makes for good news for the formwork industry. Automated self-climbing formwork systems that can be lifted up and coming with a host of features including, wide and protective platforms, apart

While certain factors are not within the control of those in the formwork industry, such as investment in infrastructure or realty projects, there are certain aspects that suppliers feel need to be done in order to give fillip to the industry. Increasing cost of steel, sales tax and excise duty are for instance, key factors that are inhibiting the growth of the industry. With formwork systems being today made mostly out of light weight and strong materials such as aluminium, higher levies have become a stumbling block, since they add to the end cost of the product. According to industry analysts the least that the government can do is to help suppliers procure raw materials at reasonable rates that would go a long way in helping suppliers keep their prices competitive. There is no doubting the potential of the

“In terms of market value, formwork market in India is approximately ` 14 billion, out of which modern formwork has a 15 percent share”

Surajit Ray Managing Director & Country Head, ULMA Formwork Systems India Pvt. Ltd.

industry though. As rightly pointed out by Mr.Surajit Ray ,Managing Director & Country Head, Ulma India, who in an interaction with The Masterbuilder stated that, “In terms of market value, formwork market in India is approximately ` 14 billion, out of which modern formwork has a 15 percent share,” figures which show the sheer magnitude of the untapped market. The predominantly unorganized nature of the market is another challenge that needs mention here. There have been calls from industry experts for setting up of specific certification bodies for construction industry product segments such as formwork systems, since otherwise quality could take a severe beating. A rapidly evolving customer is perhaps the most important challenge that suppliers are facing today. Customers are demanding equipment that is easier to handle, reusable, helps them in adding to the efficiency and sustainability of the construction process and all this at a fair price. With market conditions expected to show signs of recovery as the economy enters a crucial phase as part of the 12th Five Year Plan period, it remains to be seen as to what direction the formwork industry takes in the next five years. Picture Source

Rising cost of raw materials is an an area of concern for formwork suppliers

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http://www.beton.org http://www.rmdkwikformnews.co.uk

Maruti Steel Fab

Formwork Failure

Pic source: http://www.ppconstructionsafety.com

Formwork Failure: Cases & causes Special Correspondent

C

ollapse of concrete structures during construction has been happening since concrete has been placed in formwork. Cases and causes of these type of failures have been documented and recorded in many texts, articles and journals. This article will try and focus on a few of them from the available reports, starting with The New York Coliseum on May 9, 1955, 2000 Commonwealth Ave. on January 5,1971, Skyline Plaza in Bailey's Crossroads on March 2, 1973, The Harbour Cay Condominium in Cocoa Beach, Florida in March 1981 and ending with The Tropicana in Atlantic City on October 30,

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2003.The focus will be on what has been learned over time from these failures and what has been done to keep these type of tradgedies from occurring in the future. Although there were many cases of concrete failures during construction prior to the New York Coliseum collapse as illustrated in (McKaig 13-27, 1962), only a few will be looked at after this point because of the changes and progressions being made in the construction industry at this time in history. (A) New York Coliseum on May 9, 1955

Formwork Failure

The construction method was a flat plate waffle slab with solid slabs at the column caps. It was one of the first times the use of motorized buggies had been used in the pouring of this type of structure. The floor that collapsed was the first floor above grade supported on two tiers of shores at

Figure 2: Typical flatplate with uniform distributed loading

Figure 1: N.Y. Coliseum Collapse, National Archives

a total of 22' high. It can be seen from Figure 1 how collapse happened. The buggies weighed about 3000 lb loaded, ran at about 12 mph, and there were eight of them at the time of the failure with about 500 cubic yards of concrete already placed. The investigation that followed put the blame solely on inadequate provisions in the formwork to resist lateral forces, it even went on to say that "if there had been sufficient diagonal, horizontal, and end bacing of the temporary supporting structure, the collapse could have been prevented entirely,...", (McKaig 15-16, 1962). After the collapse the district attorney called attention to the lack of inspections and made recommendations to revising the building code with respect to formwork because of the new advances.

Figure 3: Punching shear failure diagram

(B) 2000 Commonwealth Avenue: January 5, 1971 This was a progressive collapse of a cast-in-place reinforced concrete flat-slab structure. Punching shear was determined to have been the triggering mechanism but the real problem was in the numerous errors and omissions by every party involved in the project (Delatte 133-143). The investigating committee determined that if the construction had had a proper building permit and had followed codes, then the failure could have been avoided (Delatte 142) (See Figure 2 and 3 how failure occurred). Some of the problems leading to the collapse are -

Not following the structural engineers specifications for shoring and formwork Lack of concrete design strength Lack of shoring or removed too soon

Figure 4: Skyline Plaza at Bailey's Crossroads, National Archives

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Improper placement of reinforcement Little construction control on site Owner changed hands many times Almost all jobs were sub contracted No architectural opr engineering inspection done Inadequate inspection by the city of Boston The general contractors representative was not a licensed builder Construction was based on arrangements done by the subcontractors No direct supervision of subcontractors


169

Formwork Failure

(C) Skyline Plaza: March 2,1973 Skyline Plaza (See Figure 4) in Bailey's Crossroads is an example of a catastrophic collapse of a 30 story cast-inplace reinforced concrete structure. This was also a flatplate design structure that failed due to punching shear on the 23rd floor and resulted in a progressive collapse. Some of the reasons for this failure again were 1) premature removal of shores and reshores, 2) insufficient concrete stength, 3) no preconstruction plans of concrete casting, formwork plans, removal of formwork schedules, or reshoring program (Kaminetzky 66-67). (D) Harbour Cay Condominium: March 1981 Built just 10 years after 2000 Commonwealth Ave. and 8 years after Skyline Plaza, was another cast-in-place reinforced concrete structure that collapsed during construction. It was determined that the most important factor towards its failure was a design error coupled with a construction error of the wrong size rebar and chair height. The designer never performed any calculations to check for punching shear, the most common form of failure in these type of structures (Feld & Carper 18).

walls with the required reinforcing steel. Built without the necessary steel, it is no wonder it collapsed like a house of cards." (pr newswire) The vertical columns left standing and the fact that the floors were not connected implies that this was another punching. Refer Figure 5 for the collapse picture. Codes & Regulations Codes in Place ACI, The American Concrete Institute's origins started in 1905 with its first building code published in 1910 and changing its name to the current designation in 1913. ACI's first design handbook came out in1939 and the first building code titled ACI 318 came out in 1941. The beginning volumes of ACI were less tha fifty pages with the current code specification being nearly 470 pages of design specifications and commentaries (ACI 318). This clearly shows the history of ACI is closely tied to the ever changing demands of concrete construction and technology. The ACI sees itelf as an expanding, alert,and informed organization prepared to stimulate imaginative applications of concrete and better knowledge of its properties and uses, and will take an increasingly active part in solving problems affecting the public welfare (History of ACI). Lessons Learned (A) New York Coliseum on May 9, 1955 From this failure the construction industry learned that shoring systems should be well braced to resist lateral loads and to consider the effect of power or motorized buggies/carts on the formwork (Auburn University). (B) 2000 Commonwealth Avenue: January 5, 1971

Figure 5: Tropicana Casino; Parking Garage Picture taken from www.CTLGroup.com

(E) The Tropicana Casino parking garage in Atlantic City, N.J.: October 30,2003 The structure collapsed during construction killing another four construction workers and and leaving more than 30 others injured. Larry Bendesky, Mongeluzzi's partner of the Philadelphia law firm Saltz, Moongeluzzi, Barrett & Bendesky, P.C, the lead counsel for the litigation with Paul D'Amato of the D'Amato Law Office and a member of the trial team, said that "the simple explanation of the cause of the collapse is that the floors were not connected to the

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From 2000 Commonwealth Ave. the industry learned that this type of failure is a critical failure mechanism for flatplate-slab concrete construction. Structural safety depends on adequate slab thickness, proper placement of reinforcement, and adequate concrete strength (Delatte 144). (C) Skyline Plaza: March 2,1973 Six lessons learned from the colloapse of Skyline Plaza at Bailey's Crossroads are listed in (Kaminetzky 67) -

the contractor should prepare formwork drawings showing details of the formwork, shores, and reshores.

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The contractor should prepare a detailed concrete testing program, to include cylinder testing, before stripping forms.

Formwork Failure

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The engineer of record should ascertain that the contractor has all the pertinent design data (such as live loads, superimposed dead loads, and any other information which is unique to the project).

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Inspectors and other quality control agencies should verify that items 1 and 2 above are being adhered to.

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Uncontrolled acceleration of formwork removal may lead to serious consquences. 6) Top and bottom rebars running continuously within the column periphery must be incorporated in the design.

(D) Harbour Cay Condominium: March 1981 The Harbour Cay Condominiums presented the industry with six more lessons learned in this type of construction also listed in (Kaminetzky 77-78). This tradgedy happened only eight years after the Skyline Plaza tradgedy and yet some of the same lessons are listed again, they are -

A punching shear strength check s critical to the success of a flat-slab, since punching shear is the most common failure mode of concrete slabs.

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Minimum depth of a flat-slab must be checked to assure proper strength and acceptable deflections.

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Reinforcing bars, both at the top and at the bottom of the slab, should be placed directly within the column periphery to avoid progressive collapse. This can easily be accomplished routinely in all flat-slab jobs at no additional cost at all.

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Proper construction control must be provided in the field, including design of formwork by professionals. This must include shoring and reshoring plans, procedures, and schedules, with data on minimum allowable stripping strength of the concrete.

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When there are failure warning signs of any type on a construction site, work must stop. All aspects of the project must be carefully evaluated by experienced professional help. Immediate evacuation of the structure must be considered.

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Special care must be taken during cold weather to evaluate the actual in place strength of the concrete. It is also a fact that the level of construction carelessness increases in the winter months.

(E) The Tropicana Casino parking garage in Atlantic City, N.J.: October 30,2003 The Tropicana lessons learned have not yet been published in any documented form, but from articles such as the one from ASQ Newsletter published in the summer of 2004, one can reasonably determine that all of the above lessons learned will be revisited. The article states that all of the errors were remarkably simple engineering error.

Contractor failed to tie rebar in the frames floor beams to the columns and shear walls in several places was only one reason as listed in (ASQ Newswire 11-12). Statistics Statistics released in 1984 by the National Safety council reported over 2200 deaths were reported for the construction industry for that year, and 220,000 disabling injuries, the largest total for the eight major industries surveyed (Carper 312). Over $1.6 billion is lost annually in the U.S. due to construction accidents (Carper 312). Forty-nine percent of falsework collapse happens during concrete placing (Hadipriono & Wang 115).Untimely removal of falsework is the second most significant event related toconcrete failure (Hadipriono & Wang 116). Investigations prove that many accidents causing thousands of dollars worth of damage could have been prevented if only a few hundred dollars had been spent on diagonal bracing for the formwork structure (University of Washington). Conclusions OSHA, ASCE, and ACI have all responded to these as well as many other accidents and issues with activities, publications and codes aimed at improving construction safety and the welfare of our construction workforce; however, these organizations alone cannot be responsible for all construction related activities and failures. The safety record in the construction industry can be and must be improved in all phases. As C. Roy Vince has stated, many construction accidents are the result of ignorance, carelessness, and greed (Carper 133). The lessons learned from above being repeated over and over again can only point to the fact that this statement is precisely true. "As long as structures are constructed by humans, using imperfect materials and procedures, failures are likely to continue. Many of these failures will occur during the process of construction, endangering the lives of construction workers." (Carper 143) There is no way to break everyone of their bad habits but awareness has to be raised and the consequences have to be sharply increased. More focus has to be placed on required education of all construction personel beyond certain levels of responsibility, this is to include the workers themselves who are actually assembling these structures. Better licensure requirements, more stringent inspections, and increased factors of safety during construction (because it is at this time when the structure will be likely to see its most significant loading), should also be considered to help prevent these tragedies from reoccurring. From the initial design phase to maintenance of the structure after


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Formwork Failure

completion everyone involved needs to pay strict attention to all details and warning signs of impending failures. There can be NO SHORTCUTS if we are to protect the safety and lives of the individuals who provide us with all of the essential structures in our lives. Most often it is not their mistake that cost them their life and the misery of the families who lost them too soon.

newyork%20coliseum.htm> (2009), (Sept. 18, 2009) -

Charles D. Reese and James Vernon Eidson, (2006). "Handbook of OSHA Construction Safety and Health" pp. 181-183

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Fabian C. Hadipriono,1 M. ASCE and Hana-Kwang Wang2, (March/April 1986). "Analysis of Falsework Failures in Concrete Structures" J. Constr. Engrg. Mgmt. 112(1), pp. 112-121.

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Jacob Feld and Kenneth L. Carper, ((1997) "Construction Failure" pp. 242-274 Kaminetzky D. (1991). "Design and Construction Failures" Lessons In Forensic Investigations pp. 67-78

References -

American Concrete Institute. "History of ACI" (October 10, 2009)

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M. ASCE, (August 1987). "Structural Failures During Construction" J. Perf. Constr. Fac., ASCE, 1(3), pp. 132-144.

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ACI Committee 318, (2008). ACI 318-08 "Building Code Requirements for Structural Concrete and Commentary" pp. 81-82

McKaig T. (1962). "Building Failures" Case Studies in Construction and Design Norbert J. Delatte Jr., Ph.D., P.E. (2009). "Beyond Failure" Forensic Case Studies For Civil Engineers pp. 129-155

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ACI Committee 318, (1963). ACI 318-63 "Building Code Requirements for Structural Concrete and Commentary" pp. .

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Arthur H. Nilson, David Darwin and Charles W. Dolan, (2004). "Design of Concrete Structures" pp. 12-17

PR Newswire. "$101 Million Settlement in Deadly 2003 Tropicana Parking Garage Collapse That Killed Five Workers" < http:// www.prnewswire.com/news-releases/101-million-settlement-indeadly-2003-tropicana-parking-garage-collapse-that-killed-fiveworkers-58264282.html> (October 10, 2009)

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The ASQ Newsletter. "Extracts from Engineering News Record" OSHA Report Claims that Atlantic City Garage Contractors Failed to Tie Rebar and Properly Shore (summer 2004), (October 10, 2009)

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University of Washington. "CM 420 Course Lecture 1" Temporary Structures (Spring Quarter 2002), (Sept. 18, 2009)

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Zallen Engineering. "Collapse of Flying Formwork During Concrete Placement" (July 2002), (Sept. 18, 2009)

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http://failures.wikispaces.com/2000+Commonwealth+Avenue++Boston

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Auburn University. "Lateral Stability of Structures" New York Coliseum

Cosmos Construction Machineries & Equipments Pvt.Ltd

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Modern Formwork Systems: A Ringside view of the Variety of Formwork Systems Available Today M.K. Prabhakar, Associate Editor

I

t won't be a misnomer to say that perhaps no other industry has been impacted by advancements in technology as the construction industry in the last three decades or so. In fact, with the economic boom that was witnessed in several parts of Asia (still continuing in many, despite economic slowdown) during the 1990s

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and South America, it could be stated that the 1990s and the following 2000s have been decades of construction. Several countries were and are even now vying for the title of 'construction site 'of the world. Gone are the days when mega projects were the domain of only the superpowers. Today, even small countries have given vent to their


ambitions and coming out with outstanding civil engineering achievements. No longer are skyscrapers the fiefdom of US. Even a tiny country like Taiwan or South Korea boasts of gleaming towers. Better quality buildings are being at a faster speed and importantly in a cost effective and environment friendly manner, all

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such as cost, speed and efficiency were the driving force behind the growth of the global formwork industry, the last decade has seen increasing emphasis on sustainability add to their demand. The modern formwork systems are a far cry from the bespoke timber formwork that used to be the staple of the construction industry earlier. Intense competition has meant that suppliers are always on their toes and coming out with product innovations to garner their share of the market. Let us take a look at various types of formwork systems that are being used, their key application areas, their advantages and their sustainability quotient. Table or Flying Form Systems

The mobility factor, along with the relatively easy installation means that these system are widely used in construction projects where repetitive structures, where flat slab and slab layouts are involved. Some of the application areas include residential apartment units and commercial buildings. Typically in cases where large floor layouts are the need, then this type of formwork system holds the best bet. Since the assembled units can be moved easily, it ensures speedy construction, apart from the high

Picture Source: Doka International, www.Doka.com

Let us begin with the 'Table' or 'Flying' form systems. These systems consist of slab formwork “tables” that are reused on multiple stories of a building without being dismantled. The assembled sections are either lifted per elevator or using cranes from one story to another. 'Fillers' are used to fill gaps between the tables and walls.

Table formwork systems are typically used in large floor layouts

thanks to advancements in one area Formwork systems. The rapid advancements in the field of formwork, along with the innovations in concrete as a material has led to a revolutionary change where safer, quicker , sustainable and more efficient construction is possible these days. While during the early 1990s factors

An assembled Table section formwork being lifted by a crane


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construction operations. This automatically means reduction in wastage, time and labour costs. Moreover, adding to their sustainability factor is the fact that quite often disposable forms can be recycled and used again. Horizontal Panel Systems

The highly engineered nature of a system column formwork ensures greater construction efficiency

quality surface finish. The system also scores high on the sustainability front since it can be reused. Moreover, the wastage generated is negligible as compared to the traditional formwork systems that were earlier used. Another key factor that should be noted is that with the table formwork system time is also saved, which in turn leads to cost savings , particularly in the case with structures with flat slabs. Moreover, the engineered nature of the formwork and the repetitive process ensures that there is almost negligible wastage, making it a favorite with contractors.

then stripped and moved to the next position. In certain cases the formwork systems may be left for a longer period of time for added curing. One of the major advantages with column formwork systems is the highly engineered nature of the formwork. What this in turn means is that they ensure greater control over the

System Column Formwork System column formwork has gained in popularity due to the acute shortage of labour in recent times. Modular in nature and allowing for quick installation on site, column formwork systems are now available in a variety of materials. Depending on the concrete finish that is required, contractors can now choose from aluminum or steel column formwork systems these days. R & D has led to several product innovations. Today different formwork systems for different column sizes can be easily assembled on site. Their entire working process is also simple. Once the concrete is poured and hardened, the formwork is

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Lightweight formwork systems are in demand


Advancements in the field of formwork have seen several new types of materials being experimented with making an entry into the market. Smaller, lightweight modular systems have nowadays become the norm. These systems are being made from a variety of materials such as fiber glass, aluminum and steel, apart from other customized options. These easy-tohandle systems enable quicker erection, saving precious time and money. Suppliers have also been concentrating on reducing the number of different components in formwork systems, which in turn allows for a quicker installation process. Horizontal panel systems usually consist of a series of interconnected falsework bays and pre-formed decking panels and are typically used for slab construction.


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The lightweight nature of the components is perhaps the biggest advantage with horizontal panel systems. They can be moved around the site with relative ease, as compared to traditional formwork. Adding to it is the engineered nature of the formwork which ensures reduced wastage. Another major advantage with lightweight formwork systems is safety, since working from height is not necessary, as erection work can be carried out from below. Vertical Panel Systems Vertical panel systems, because of their flexible nature can either be smaller modular components or larger crane-lifted systems that are used in the construction of standard columns, concrete walls or perimeter basement walls. They are used for forming vertical elements and are usually modular in nature. Consisting of a steel frame, they are easier to assemble, in turn leads to reduced labour costs, making them a more cost effective option than traditional formwork systems. Their adaptability to varying wall heights and structural geometries,

along with the fact that their assembly is less labour intensive and simple has been behind the popularity of vertical panel systems. The easier erection process aids in expediting the construction process, apart from the fact that the engineered nature allows for precision and superior control of operations for the on-site team. Adding to the sustainability factor is the fact they can be used repeatedly, after an easy cleaning process. Jump Form Jump form systems are increasingly becoming popular globally, thanks to the spurt in high-rise construction. Jump form, also referred to as climbing form, comprises of formwork systems complete with working platforms that supports itself on the concrete that has been cast earlier. It therefore does not rely on support from the building. They are typically used in construction of multi-stored vertical concrete elements. Some of the concrete elements that are constructed using jump form systems include, core walls, shear walls, bridge pylons and lift shafts. The use of jump form systems helps in cutting down on

lb

Vertical panel systems are adaptable to various structural geometries

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Spurt in high-rise construction has driven demand for climbing formwork systems

labour costs, while increasing construction efficiency. The jump form modules can be joined together to suit different construction geometries. Latest advancement in the field has been the advent of self-climbing formwork systems, that do not require the help of a crane to be relocated to the next construction level and climbs on rails by means of hydraulic mechanism. Climbing formwork is usually used in the construction of buildings over five storeys. Self-climbing, automated systems are generally used in the construction of buildings with more than 20-25 floors. Based on the site conditions, there are also instances when a combination of self-climbing and crane-handled jump form systems is used. The engineered nature of the formwork means that jump form systems allows for better control of the construction process. Repetitive use is possible adding to the cost-effectiveness of the construction process. Apart from offering enhanced safety, the use of jump form systems also ensures minimal concrete wastage and helps contractors to stick to tight project deadlines.

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allow the form to 'slip' to the next level above, apart from supporting the freshly poured concrete above it. Typically slipform systems rise at a rate of about 300 mm per hour and with prudent planning, high rates of production are possible. Fine tuning of operations in the site is facilitated by the repetitive and continuous nature of work. This also leads to reduced concrete wastage. The integration of work platforms in the formwork systems is another advantage that apart from ensuring safety also makes optimum utilization of work space available in a construction site. Given the slew of advantages it is not surprising that slip form systems are a preferred choice of contractors nowadays. Tunnel Form

Slip form systems enable high production rates

Slip Form Similar to jump form systems, this type of formwork rises continuously, supporting itself on the core. Slip form systems are typically used for the construction of core walls in skyscraper projects. Since very little crane time is required, they are used for the construction of stair shafts and lift shafts in high-rise structures. Slip form systems

rely on the quick setting properties of concrete and require balance between quick setting capacity and workability of the concrete. While the concrete needs to be workable enough to be placed into the form and packed, it should also be quick setting so that it emerges from the form with strength. Moreover, the freshly set concrete should, apart from its strength, also

Tunnel form systems are among the latest innovations to have hit the formwork industry. The use of repetitive cellular structures to construct both horizontal and vertical elements together is something that has got the potential to revolutionize the construction industry in countries like India. The fact that they enable construction of walls and floors together make the process ideally suited for both high and low raise housing. In fact, the technology can play a key role in the promotion of affordable housing projects in a country like India. Longer tunnel lengths can be achieved joining individual tunnel units together. Easy to clean and reuse, the use of tunnel form systems also enables high quality surface finishes. Engineers are also assured of high dimensional accuracy of structures. The repetitive nature of the construction work is another plus point with this type of formwork system, adding to its other advantage of requirement of a very small team on site. Picture Source

Construction cycles can be as low as 24 hours with tunnel form systems

www.kildownet.co.uk, www.alibaba.com www.uni-span.com.au, www.doka.com www.tfl-gr.com, www.nb-luowen.com www.water-technology.net www.made-in-china.com


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Focus Fabric Formwork

Picture Source: www.matsysdesign.com

Fabric Formwork: Sky’s the Limit Special Correspondent

F

abric formworks for reinforced concrete construction and architecture is an emerging technology with the capacity to transform concrete architecture and reinforced concrete structures. The natural tension geometries given by flexible fabric membranes provide extraordinarily light and inexpensive formworks, some using hundreds of times less material than conventional formworks, and some providing zero-waste formwork systems. The flexibility of a fabric formwork makes it possible to produce a multitude of architectural and structural designs from a single, reusable mold. The use of a permeable formwork fabric produces improved surface finishes and higher strength concrete as a result of a filtering action that allows air bubbles and excess mix water to bleed through the formwork membrane. A brief history According to the International Society of Fabric Forming,

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the first practical applications for fabric formwork were introduced in the mid-1960s for erosion control and to line ponds, although there are several patents for 19th- and early 20th-century fabric forms. In the 1970s, the Spanish architect Miguel Fisac used thin plastic sheets as formwork for textured wall panels. In the late 1980s and early 1990s, three men, each on his own, invented a variety of techniques for fabric-forming aboveground structures. Kenzo Unno, a Japanese architect in Tokyo, invented a fabric formwork system for in situ cast concrete walls. Rick Fearn, a builder and businessman in Canada, invented a number of fabric formwork techniques. This led him to develop a series of foundation footing and column products now manufactured and sold by Fab-Form Industries in Surrey, British Columbia, Canada. He is president of the company. Mark West - an artist, architectural educator and builder who is now the director of the Centre for Architectural Structures and Technology

Tac System Formwork Sdn Bhd


(CAST) at the University of anitoba's Faculty of Architecture in Winnipeg - invented a series of techniques for constructing fabric-formed walls, beams, columns, slabs and panels. CAST is the first research center dedicated to fabric formwork technology and education. Visualizing the end result "Fabric is so much more efficient than plywood (for forms), but the industry is slow to change," says Rick Fearn. "It's staggering how long it takes to get new ideas into the marketplace." He thinks the biggest stumbling block to fabric formwork's acceptance is that many contractors cannot picture the end result before they start. "(Unlike rigid formwork), it's just a loose piece of fabric. What you get is not what you see." To help contractors visualize an end product, Fearn has a computer program that predicts the shapes fabric forms will produce. He's hoping that as more contractors accept computer-generated virtualreality scenarios, fabric formwork will grow in use. "Fabric is a tension membrane," Fearn says. "If you use a different fabric, it will give you a different texture, but the shape will be the same." Also, some fabrics aren't coated, so they let excess water bleed out, he notes. This can make fabricformed concrete products stronger than those made with traditional lumber forms. In a world where resources are dwindling, he notes, fabric forms, like the ones he sells for columns, just make good sense. Fast-Tubes, made from high-strength polyethylene, come in 120-foot rolls that easily fit behind the seat of a truck and can be cut to any length with minimal waste. Fabric formworks are such a green product and so efficient. They take up 1% of the space cardboard does and they are 1/10 the weight. Also unlike cardboard, there is no waste to be hauled to the landfill after the column forms are trimmed to size or when the forms are stripped. "Fast-Tubes can be put under a slab after they are stripped. They act as a moisture protector." Besides allowing contractors to form sturdy columns of varying lengths - Lawton used Fast-Tubes to make 29-foot columns for a treehouse he built in Vermont - Fearn's fabric-formed columns can be easily decorated by simply tying ropes or putting bands around the forms while the concrete is still wet.

formwork. Morover where space is a concern, stocking and keeping of rigid formwork will be a major concern. Since most of the fabric formworks are made for one time use only, they can be kept after concreting which will facilitate in curing of the concrete. If any kind of aesthetic treatment is required to be given in the structure fabric formwork is the only option as it is very tough with rigid formwok and in some cases it is impossible also. End product using fabric formwork A flexible fabric mold awakens concrete to its original wet, plastic nature by naturally producing concrete members with complex sensual curvatures. The sculptural and architectural freedom offered by this method of construction is matched by new possibilities for efficiently curved structures. Research at CAST has produced simple methods for forming beautiful and efficient beams, trusses, panels, vaults, slabs, and columns. The Centre for Architectural Structures and Technology (C.A.S.T.) is fundamentally interested in finding simple ways to reduce the amount of material consumed in construction, while at the same time, making these constructions more beautiful. C.A.S.T. is also committed to making these methods accessible to as many people as possible. The end product is divided here into two parts viz. (A) Architectural application, (B) Strutural Application. (A)Architectural application Fabric formwork can be used to give tough architectural shapes to the structural member very easily. Figure 1 shows typical surface of a fabric cast panel and Figure 2 shows a branched column made with fabric formwork. Fabric forms can be used to produce complex concrete

Flexible fabric vs. hardened forms The primary differences between both the formwork is ease of errection.While rigid formwork needs more time to errect. Also lot of staging and design work is needed for rigid formwork which Is not required for flexible formwork. One more striking advantage with flexible formwork is that any shape can be designed and made using fabric formwork. The same fact is supported by the all the Figures in the entire storey. Use of fabric formwork saves lot of manpower cost and saves lot of energy for preparation of the rigid 184


Figure 1:Surface detail of a fabric-cast panel

Figure 2:Branching column formed in a geotextile form-liner


shapes that would be extremely costly or nearly impossible to create with traditional rigid formwork. Anne-Mette Manelius, an architect and doctoral student in Copenhagen, Denmark, made this chair as part of her thesis work on fabric formwork for concrete. She wanted the softlooking chair to fool sitters (Figure 3).

ties to make "buttonholes" to placing a brick under a fabric form to make a relief. Kenzo Unno, a Japanese architect in Tokyo, devised methods to cast beautifully shaped walls with thin, flexible textile sheets. These methods are collectively called "Unno Reinforced Concrete (Shown in Figure 4)."

Figure 3: Chair produced with fabric formwork

Green, clean, relatively inexpensive and incredibly practical, fabric formwork can be used with concrete to produce structurally efficient and architecturally compelling components in all shapes and sizes, ranging from footings, columns and beams to walls, sinks, furniture and an array of accessories "It's allowed us to create masonry architecture using very simple skills," says Sandy Lawton, owner of ArroDesign, a design/build construction company in Waitsfield. With a background in carpentry, Lawton says, he found rigid formwork complicated and labor intensive. "Fabric formwork has given us the freedom to do complicated structural work in a very different way that's not complicated at all. That's the bigger advantage. There's a lot more flexibility with this system." Fabric formwork also has benefits from a sustainable viewpoint, Lawton says. "Fabric formwork basically reduces the amount of everything required to construct something - placement, storage and even building the forms. There are huge savings every step of the way." Also, he points out, depending on the type of fabric you use for the formwork, you can get a really nice finish. "You don't have to go behind and refinish." Instead of using rigid forms made from lumber, plywood, cardboard, steel or aluminum, fabric forms use a flexible textile membrane to form concrete in place. Wet concrete is poured into a tensile membrane, which produces efficient structural curves and extraordinary surface finishes. The shape is determined by how the material is restricted. This can happen in a number of ways, from creatively using form

Figure 4: Walls casted with Fabric formwork

Figure 5 shows a thin GFRC stingray sink created by students of Brandon Gore of Gore Design Co.

Figure 5: The 1-inch-thick GFRC Stingray Sink

(B) Strutural Application Here the use of fabric formworks in various structural members is shown. Figure 6 and Figure 7 shows casting of a isolated footing and slab footing using fabric formwork. The fabric comes in rolls of certain widths and it is simply cut on site to suit the size needed. Apart from normal tools for cutting and fixing the braces and perimeter frame, the only extra items are a Stanley knife and a staple gun. The fabric is cut neatly with the knife and staple to the timber. There is a very simple method of cutting the fabric at the


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corners, and when it is simply stapled in position that it, in effect, holds the corners together just as strongly as normal methods. Before the pour, a sheet of standard plastic vapour barrier is laid on top of the fabric to stop the footing absorbing moisture if it is required. It can be noticed from Figure 6 and Figure 7, that no movement at the top and a slight bulging at the bottom is there in the freshly concreted isolated footing.

Figure 6: Fabric formwork used for casting isolated footing in a construction site

Figure 9: Fabric Formwork - Stripped column

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The fabric tube is simply cut to length with a Stanley knife.

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In the manufacture, tabs are made vertically along a center line.

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The loose sleeve of fabric is fitted over the rebar.

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The tabs are then nailed to a straight length of 4" x 2" timber.

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The 4" x 2" timber is then positioned, and braced to hold it plumb.

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For the first foot or so a guy hold the base of the tube in the correction position with a boot on either side.

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During the pour, it is possible for a guy to feel and guide the rebar cage, to make sure that it is in the correct position.

A system for forming round concrete columns using fabric formwork

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Figure 8 and Figure 9 shows round various stages of casting of round concrete column. It can be very easily seen the end product finish in Figure 9 and also the ease of casting from the other Figures ( from Figure 8 (a) to (c) ).

Unlike conventional formwork, because this is a throw away, one off system there is never any reason for undue haste to strip the formwork.

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Therefore the fabric can be left in position to act as a perfect curing membrane

Figure 7: Fabric formwork used for casting isolated slab footing in a construction site

However if there is a doubt that whether this system can work for higher columns, then Figure 10 shows the 20ft tall column ready to be poured in one hit. The project for a church in Nicaragua in Central America. The concrete was mixed by hand on the site and lifted up by hand. In itself, this was probably a good thing as the slowness of the pour would mean that the concrete at the bottom would be stiffening up nicely as the height increased, reducing the theoretical hydrostatic pressure. Conclusion

Figure 8: (a) Column ready to be poured, (b) Column pouring in progess, (c) column pouring completed

This method of casting column is beneficial because of following reasons -

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The fabric come ready made up in tube sections to form the desired diameter of the column.


It is very essential to use fabric forms and rebar in an area where wood is scantily available. Fabric is a very forgiving material.However one should remember that fabric formwork is not as uniform as standard formwork. Engineers had to create some structure to give the appearance of what they wanted, but in the same breath it gives us a lot of design freedom. It is really an exciting medium. As for fabric formwork's limitations, "It's wide open. No one have tested its limits yet.

Ambattur Scafolding Company

Tunnelling Construction Chemicals

The Influence of Construction Chemicals on Tunnel Durability

Willie Kay Managing Director of WAK Consultants Pte Ltd / WAK Technologies Pte Ltd , MC Bauchemie Muller GmbH & Co

This paper looks at the role construction chemicals in the Tunnelling Industry. Advances in both Tunnel boring machine technology (TBM) and ground conditions have accelerated the need and growth of specialised material. Specialised additive and admixtures have revolutionised the durability and production of precast segments. The advancement of Alkali free shotcrete accelerators has enabled much safer working conditions. The uses of supplementary cementitious additives have allowed high build high strength concrete tunnels by robotic spraying. This paper however will look at the role of injection resins in tunnels with case histories. Injection Systems Injection systems in tunnels and underground constructions are now often considered in the planning and design stage. They can be a means to simplify construction, enhance safety, and control potential leaks or many other applications. The reason for this change is due to advances in materials in terms of set times in resin to particle sizes in cement suspension. Equipment technology in mixing has improved and pumps are now capable of handling just about any material even at tropical ambient temperatures around 35oC.

Figure 1

Engineers and clients need documentary proof of materials consumed and at what pressure to ensure correct grouting and this equipment is now readily available.

negligible pressure on the substrate. Many of these products have both CE and REAch compliance. Table 1 shows some typical properties of a gel material.

Injection resins based on polyurethane have been around for more than thirty years. In general these were a single component with an accelerator and reacted with water. There were and are many manufacturers with varying quality and properties. Figure 1 show a high quality water reactive resin foamed to approximately 35 times its original volume. Newer technologies have two part polyurethane bases and have properties from highly elastic to highly rigid elastic. New technologies in gels allow swelling of up to 30% with

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Thixotropic Gels Swell up to 30% Excellent adhesion to most substrates Ductile up to 300% (see figure 2) High tear resistance Variable set times from less than 10 second to minutes Table 1. Typical Properties

Certification REACh is the uniform chemical legislation with a strong


focus on the protection of human health. Companies registered can be checked on the internet by contacting Helsinki. All the injection products we have been discussing all have REACh certification. Polyurethane Injection Resins (Elastomer) Polyurethane and Gel Technology have made major advances due to understanding the critical nature of mix ratio, mixing technology and advancement of twin line pump technology. The term polyurethane is very generic and does not reflect the technical changes that have taken place over the last twenty years. The term elastomer is adopted to describe the material as it technically describes the material function. To many people, polyurethane is a brown liquid that foams and stops leak. This statement is simplistic, as it does not reveal some of the key properties of a water reactive resin. In order to fill a void and stop water ingress, of the following properties are needed. -

Expansion of the material in contact with water

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A stable dense foam

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Non Shrinkage after foaming

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Closed cell structure to prevent water permeation

To achieve all these properties with a single component water reactive resin is impossible under all conditions. The foam density will depend on the amount of water and reaction time. The expansion will vary with the specific environmental conditions at each project. Due to these constraints, Europe and specifically Germany have adopted a two-stage process of injection to ensure

permanent leak sealing. In applications of high water inflow a water reactive open cell foaming resin is first injected as initial seal. This is ten followed by a second injection using a two part elastomer resin, which will penetrate the open cell and give a permanent watertight seal. This method is adopted from the German Training Council and German Concrete and Construction Association Deutscher Beton UndBautechnik Verein e.V. (DBV) for injection of water leaks. Two part elastomer resins have customisable stiffness properties and can be engineered from elastic and flexible, to strong and semi-rigid. The ability to adjust the setting time is of great importance to ensure complete penetration of the crack as void viscosity is another critical factor and this will be discussed later in his paper. Table 2 shows some basic properties achievable in the market today. Differing Properties of Elastomer Resin Std Pot Life Elongation Strength (N/mm2)

Long Life

UW

30 secs 45 mins 43 secs Rigid force transmitting 60

60

80

NV 35 mins 100% Compressible

Viscosity (mPas) Table 2

Hydro-Structure Resins The name hydro-structure is used to dissociate these resins from the toxic acryl gels, which has caused major environmental problems in Europe. All the resins discussed and described in this paper comply with the highest standards of non-toxicity in contact with potable or drinking water. These resins cross-link and depend on water migration for long-term performance. The latest generation has "thixo" or skinning effect which makes them an ideal solution for buried leaking joints in car parks, stations and other underground structures. The ability to be pumped into very specific locations and then set, gives an ideal method of repairing joints and damaged membranes. The viscosity of these materials is very low thus making penetration into tiny voids and fissures very quick, which is impossible to achieve with a high viscosity resin. Table 3 lists some key properties. Solidification Sealing flexible Sealing swelling Hydro-Structure Resins

-

++

+++

+ dry ++ wet +++ water pressure Table 3

Figure 2. - Example of deformation

These properties have simplified the repair of leaky segment joints. "Steps" often occurs when building tunnel rings in precast concrete and this can lead to failure of the gasket with subsequent leakage. The hydro structure resins


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with the thixo agents will be able to rebuild a membrane behind the joint and effectively waterproof the ring. Skill is needed in packer selection, gel time of the resin and pump pressure. The use of Twin Line pumps with the correct mix head technology is essential. Equipment Advances in equipment technology in the last twenty years have enable resin injection to provide a long-term durable repair where previously demolition and rebuilt would have been the only answer. Twin Line pumps with varying pressure and volume outputs allow correctly trained applicators to repair almost all leak problems in tunnels. The reason why Twin Line pumps are so important and especially in tropical climates are as shown in Figure 3.

filling of the crack in the shortest possible time and to the finer parts of the cracks. Twin Line pumps are only part of much bigger technical break through as both mix head technology and online monitoring have become available. Resins which have different viscosities or mix ratios require different degrees of mixing. Some resins can be mixed in 60 seconds with a shear mixer while others require 3 minutes for complete mixing. Each resin type has a specific mixer length and this is critical if the mixed resin is to achieve the designed property. On many projects the Engineer would like to predetermine the pressures at which injection is taking place, others would like to restrict the volume of resin pumped into each packer. Other sites require a list of packers used and record of the volume, pressure and duration when the resin was pumped. All this information can be made available by using the German made control device. This equipment pictured below Figure 4 comprehensively monitors the injection process. It ensures that the machine is calibrated and should the mixing ratio be out of margin it will stop and sound an alarm. Given that the machine is in good working order it will start pumping and record pressure volume and time. At the end of a shift the tagged packers are photographed and the information down loaded. This is then transferred to a computer and a report is generated automatically. This can be co-related to the site by grid reference and crack mapping showing an as built and as repaired document. The equipment can also be used with water to carry out void surveys in structures with very heavy reinforcement when other techniques may not be suitable.

Figure 3. - Pump pressure versus injection duration

From this table one can see that the resin penetration is dependent on three factors; viscosity, time and pressure. Too high a pressure often causes more damage to the structure by re-cracking or worse. Time is something we cannot keep extending as the viscosity is increasing and the injection costs keep rising. Imagine a situation where each injection port requires a 15 minutes injection. Spacing of the injection ports could be at 250 mm centre so each linear metre of crack would take one hour to inject. The duration is also dependant on the thickness of the concrete structure. The answer is the Twin Line equipment where the resin is mixed only at the point of discharge and this enables the lowest possible injection viscosity at the packer. This allows

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Figure 4

Applicators With the sophistication of materials and equipment technology, a new approach to applicator training has evolved. Companies licensed to use the materials and equipments are required to have a government backed independent certification. This requires attending a two weeks residential course in Europe taking and passing an exam supervised by impartial and independent bodies. Manufacturers are not allowed to give this independent overview in a training course. The course is operated by the BZB Akemie and the course topics include Basics of concrete and steel, repair of concrete construction parts,


polymer and spray polymer repair mortars, and injection of cracks cavities, joint repair, surface protection systems and strengthening using carbon fibre laminates. An examination occurs at the end of the course and if successful a certification is given. After which, these licensed operators then attend specific product and machine training to ensure the total system Man, Materials and Machinery works.

with double road decks built into the central three kilometre section, relieving traffic congestion by providing 2 x 2 traffic lanes for cars connecting the city centre to the southern gateway, the KL - Seremban Highway.

Case Histories

Brisbane Road Tunnel - Case Histories

Suspended slab / Segment detail Application

North South Bypass Tunnel - NSBT

TBM Segment Installer

The SMART Project provides a storm water diversion scheme including floodwater storage and a 10 km, 11.8 m diameter bypass tunnel, sufficient to save the city from flooding in the foreseeable future. With no major flood event most of the year the tunnel a dual use was engineered,

The flood water is diverted at the confluence of the Klang and Ampang rivers into a Holding Pond. From there the water passes through the tunnel into the Taman Desa Attenuation Pond and via a box culvert discharges into the Kerayong River.


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Area of Application

Full Depth Penetration

Application Preparation SMART Tunnel Malaysia - Case Histories

Figure 5

Shaft & Joint Sealed

MC was involved in supplying admixtures for both the backfill grout and the road deck concrete. We were also involved with all grouting to stop water ingress from within the tunnel. Figure 5 and Figure 6 show two specialised injection systems. Figure 5 shows how we repaired damaged gaskets using specially developed packers and Figure 6 shows a specially developed packer for resealing leaking grout sockets.

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Figure 6

Summary As tunnel technology advances new materials have been developed to keep up with these advances and no doubt will continue in the future.


Tunnel Engineernig TBM's

Modern TBMs: Enabling the Next Wave of Infrastructure Growth in India Bhavani Bhavani Balakrishna Balakrishna

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ith sizeable investments envisaged for infrastructure sector INR 5 trillion in roads, INR 1.2 trillion in hydropower, INR 1.8 million in water and sewerage systems and INR 1 trillion in metro rail projects in the 12th plan, tunnel works are going to be in the spotlight. And with increased focus on development of world class tunnel infrastructure, the Tunnel Boring Machines (TBM) industry is expected to witness a lot of activity in the coming years.

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TBMs in India The tunnel TBMs were earlier employed primarily in the water supply sector and later in hydro-electric projects. A TBM was used first in India in 1984 for excavating a tunnel of diameter 3.5 meters under a project for the Bombay Water Supply Scheme. Although TBMs made an entry in early 1980s, conventional drill and blast methods remain predominant in India. Despite, the progress rates achieved


with such traditional methods being extremely low 7.5m to 81.0m on monthly average basis based on the size of tunnel and factors like geography, one of the main reasons for not using TBMs for such tunnel jobs was the high prohibitive cost of the imported equipment and procedures involved in import of the modern equipment. However, what was not considered was that tunneling by drill and blast methods, particularly in soft rocks, often resulted in over-breaks of the order of


metro rail projects of several metropolises in India. In fact, the Government, recognizing the significance of these machines in hydroelectric and road projects, has provided full exemption from basic customs duty and additional duty of customs (CVD) on tunnel boring machines and parts and components thereof for use in the assembly of Tunnel boring machines used in hydroelectric and highway development projects. TBMs operate in all kinds of geologies comprising hard rock, soft ground and mixed-face conditions with high overburden and high ground water pressures. The application range of soft ground machines such as earth pressure balance shields or slurry shields have allowed a considerable expansion of the application areas of shield tunneling leading to increased economic feasibility of these tunneling systems. The choice of a single or double shielded TBM depends on the type of rock strata and the excavation speed required and trailing support mechanisms. Double shielded TBMs are normally used in unstable rock strata, or where a high rate of advancement is required. Single shielded TBMs, which are less expensive, are more suitable to hard rock strata. Behind the shield, inside the finished

“The soft ground tunneling market is expandingparticularly in India and China- and we would like to meet the growing requirements of customers in these countries.“

Lok Home President, Robbins

part of the tunnel, several mechanisms for shotcreting, rock bolting, precast lining segments and steel ribs support are present. While more and more projects in India are switching to TBM technique over conventional technique, tunneling in Himalayas has always been a major challenge to project planners. The experiences of TBM in Dulhasti and Parabati have not been successful and the contractors had to fall back on drill and blast methods. The Himalayan geology is quite varying with folds and

Picture Courtesy: www.opg.com

10-15% leading to time and cost overruns. However, with focus on quality and tight schedules, use of TBMs has become imperative to achieve safe tunnelling while maximizing the rate of advance in excavation. This advantage has somewhat offset the high capital cost involved with this equipment. Since then TBMs have been used in hydroelectric projects, roads and water supply but these machines have been lately in the limelight for their role in the

Workers emerging as a TBM breaks through under the India capital, New Delhi


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Hybrid Earth Pressure Balance Machine (EPB TBM) built using Onsite First Time Assembly (OFTA). Narmada Valley, located in Central India's Madhya Pradesh state, is a drought-prone region for eight months out of every year. The Sleemanabad Carrier Canal is part of the Indian Government's Bargi Diversion Project, which will source water from the Narmada River to irrigate 250,000 acres (100,000 hectares) of land. The major trans-valley canal will stretch 194 km (120 mi) from the existing Bargi Dam on the Narmada River to arid areas. Once complete, the Bargi Diversion Project will transfer 152 cubic meters (40,000 gallons) of water per second to Katni, Satna, Panna, and Jabalpur districts, irrigating over 100,000 hectares (250,000 acres) of land. The contractor, a joint venture of M/s Patel Engineering, SEW, and Coastal Projects Limited (CPL), signed a contract with Robbins for the supply of a 10.0 m (32.8 ft) diameter EPB, as well as the back-up system, cutting tools, spares and continuous conveyor system. CPL also opted for Onsite First Time Assembly (OFTA) of the machine at the jobsite, in order to expedite the project schedule. The hybrid EPB was completed using Onsite First Time Assembly (OFTA) in Madhya Pradesh, India on March 14, 2011. A commissioning ceremony celebrated the launch of the TBM at the 12 km (7.5 mi) long Sleemanabad Carrier Canal. The launch ceremony also marked the first time OFTA has been used on a hybrid EPB. The Robbinsdeveloped method allowed the TBM to be initially assembled on location, rather than in a manufacturing facility. Critical subsystems, such as the electrical and hydraulic systems, were tested before being shipped to the jobsite. Once completed, the tunnel will have a diameter of 9.2 m and is expected to be operational in 2013.

A worker standing inside one of the tunnels created by the 14 TBM's used by India to overcome the challenges of a tight schedule for the common wealth games.

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large number of small and big faults, thrusts, shear-zones. Moreover, the rocks of Shiwaliks and Lesser Himalayas are, jointed, sheared, fragile and weak. These together make Himalayan rocks a difficult tunneling media. Experiences have suggested that TBM excavation needs meticulous planning and several problems can be avoided if a thorough site investigation is done. Almost every aspect of a tunneling project is influenced by the geology of the area. Inadequate geological investigation and poor anticipation of the nature and magnitude of problems result in delays and higher cost of construction. Faced with cost and time constraints, detailed investigations are often compromised resulting in lack of quality construction riddled with problems and time and cost overruns in the long term. Prior understanding, obtained in a correct manner, of the geological and geotechnical conditions of the site is fundamental for the development of underground works. Probe holes and the use of geophysical exploration techniques could be used to ascertain the presence of groundwater. Advanced geophysical methods like tomographic analysis and radar, though expensive, can be cost effective in the longer run particularly in Himalayas. Forward probing from a TBM driven pilot tunnel or a main tunnel is not an alternative to an adequate pre-investigation. Up to now, too little money has in general been spent on preliminary investigations. It has in fact been demonstrated that money spent on such investigations is greatly compensated by the savings made in terms of construction cost and time. The choice of TBM is another important aspect that needs a critical analysis at planning stage. The selection of the TBM should then be based on the interpretations of this geotechnical investigation report. Expert & independent advice should be sought on the selection of the type and TBM. Lastly, it is the men behind the machine that matter. An experienced


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team with a strong leader is the way forward. In India, the TBM market is largely dominated by Robbins, Herrenknecht, Hitachi Zosen and SELI. In 2008, Herrenknecht put into operation an assembly plant for tunnelling systems and service in Chennai covering an area of 40,000 square meters. Coastal Projects Limited, a Hyderabad-based tunnel engineering company recently acquired 26% stake in Italian based SELI. With increased number of tunneling projects in India expected to be implemented using Tunnel Boring Machines (TBMs), Coastal Projects stands to benefit from its association with SELI as it also designs and builds hard rock and soft ground tunnel boring machines and auxiliary equipment. In 2009, BEML Limited signed a Memoranda of Agreement with NFM Technologies for the manufacture of tunnel boring machines in India. NFM Technologies is the second largest manufacturer of TBM in the world with a global market share of 20%. Last year, Hitachi Zosen Corporation established an Indian subsidiary, Hitachi Zosen India Private Limited (HZIND) in Gurgaon to handle the giant Indian market Hitachi Zosen delivered two slurry-type shield tunneling machines to India for the first time for the Bangalore Metro subway construction project in Bangalore, Karnataka State. Projects Pula Subbaiah Veligonda Project A Robbins Double Shield TBM is

Typical 10.0m cross section of a double shielded TBM Shielded TBM's are generally used for fractured rocks with the help of concrete segments to support the unstable tunnel walls behind the machine. Double Shield TBMs have two modes; in stable ground they can grip against the tunnel walls to advance. In unstable, fractured ground, the thrust is shifted to thrust cylinders that push off against the tunnel segments behind the machine. This keeps the significant thrust forces from impacting fragile tunnel walls. Single Shield TBMs operate in the same way, but are used only in fractured ground, as they can only push off against the concrete segments.

boring tunnel No. 2 of the Pula Subbaiah Veligonda project for Coastal Projects Ltd. (CPL), of the CPL/ Hindustan Construction Company (HCC) JV. The Veligonda tunnel no. 2 is located in sedimentary rock on the western margin of the Cuddapah Basin, where a number of faults and folds make for complex geology. Rock includes quartzite with interbedded shale (60%) and shale with limestone and phyllite (40%) ranging from 90 to 225 MPa (13,000 to 33,000 psi) UCS. Two major faults are expected along with some ground

“Herrenknecht India Private Limited inaugurated the extension of its manufacturing unit (assembly hall, warehouse and steel manufacturing unit) in Chennai on December 14, 2011. As India is one of the fastest-growing markets in the Asia-Pacific region with very high demand, the factory set-up has been expanded by 2,000m² for a new assembly workshop, 830m² for the warehouse and 840m² for the steel manufacturing unit. In these facilities Herrenknecht will assemble and/or produce TBMs up to 9 meters in diameter, as well as cutting tools, project-specific jobsite equipment and will handle spare and wear part.“ Frank Hurst, Managing Director Herrenknecht India Private Limited

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water. The Double Shield machine utilizes sixty-seven 20-inch diameter back-loading cutters to combat the tough ground conditions. Specially designed drive motors allow the machine to run at a higher than normal RPM, compensating for low penetration rates in the hard rock. In squeezing ground, the cutterhead is also capable of vertical movement allowing for overboring. The machine also has a probe drill which allows for verification of geology 30 m (98 ft) ahead of the TBM. The drill is capable of 360º rotation and can alternatively serve as a grout consolidation drill. Large 40 kW (54 hp) dewatering pumps located on the back-up system have been specially designed to pump any water away from the tunnel face. As the TBM bores, it erects 300 mm (12 inch) thick concrete segments in a 6+1 arrangement, making the final tunnel diameter 9.2 m (30 ft). Muck haulage requires one of the most extensive conveyor systems ever used in India. The continuous steel cable belt, the longest single flight ever provided by Robbins, will extend 19.2


unprecedented onsite assembly. Both of the machines were initially assembled onsite using the Onsite First Time Assembly (OFTA) process. Geologic conditions consist of quartzite zones up to 450 MPa (65,000 psi) UCS, layered and separated by shale for approximately 50% of the length, with granite (160 to 190 MPa/ 23,000 to 28,000 psi UCS) for the remaining 50%. Both machines feature back-loading 20-inch diameter cutters for longer cutter life in the abrasive conditions. Other design modifications include specially designed drive motors to run each machine at a higher than normal rpm for optimal penetration rates in the hard rock. New Delhi Metro Extension Project Workers in the tunnel below the capital, New Delhi, working toward the completion of the 2nd Phase of the New Delhi Metro Extension Project

km (11.9 mi) and requires four main drives and three booster drives. The machine was assembled in just four months using Onsite First Time Assembly (OFTA). OFTA is a process that allows machine components to be initially assembled at the jobsite, rather than in a manufacturing facility, typically providing savings in terms of manhours and shipping costs. A huge Herrenknecht Hard Rock Double Shield is also currently at work on the project. The 2,800kW TBM is boring the 18.8 kilometer-long tunnel at depths of as much as 550 meters.

Pradesh government to construct a head regulator and two tunnels, including the main 43.5 km (27 mi) tunnel. On May 26, 2006, JAL awarded a complete contract with The Robbins Company for two 10.0 m (32.8 ft) diameter Double Shield TBMs, as well as conveyor systems, back-up systems, spare parts, personnel, and technical support. The first of the two machines was launched in March 2008 after an

10 Herrenknecht TBMs (EPB Shields, diameter 6,460 - 6,640 mm) proved themselves in Delhi. For example, they underpassed a major railway route without any disruptions to train traffic. Along one tunnel section, the TBM unexpectedly had to master rock formations, which meant that Herrenknecht had to deliver a new cutting wheel to the customer to pass this fault zone and avoid a TBM recovery. Two machines started tunnelling only a few meters away from the India Gate, one of New Delhi's landmarks, and continued boring beneath the government

Alimineti Madhava Reddy (AMR) Project At 43.5 km (27 mi), the Alimineti Madhava Reddy (AMR) Project will be the longest tunnel without intermediate access in the world when complete in 2012. The tunnel will transfer floodwater from the Krishna River to arid regions of India's Andhra Pradesh state, providing irrigation to 1,200 km2 (400,000 acres) of farmland and clean drinking water to 516 villages. Contractor Jaiprakash Associates Ltd. (JAL) won the USD $413 million engineer-procure-construct contract in 2005 from the Andhra

OFTA assembly site. It took a mere 4 months to complete the assembly


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district with its embassies without problems. The 10 TBMs successfully completed tunnelling with the last breakthrough occurring in October 2009, which allows to open the new metro lines to traffic in due time before the Commonwealth Games. Phase II of the New Delhi Metro Extension Project involved multiple soft ground tunnels to be bored by Robbins Earth Pressure Balance Machines (EPBMs) between underground stations excavated by cut and cover. The tunnels ranged from 8.6 14.0 m (28 46 ft) below the water table in sandy silt, silty sand and gravels. Both EPB cutterheads featured a 55% opening ratio to allow a smooth flow of muck and to avoid clogging the cutterhead. The machines used several types of tungsten carbide bits for boring in soft but abrasive ground and shaft-type screw conveyors to remove water-bearing muck. Continuously erected lining along the length of the tunnel consisted of reinforced concrete segments 275 mm (11 in) thick. Sleemanabad Carrier Tunnel The Sleemanabad Carrier Canal is part of the Indian Government's Bargi Diversion Project, which will source water from the Narmada River to irrigate 250,000 acres (100,000 hectares) of land. The contractor, a joint venture of M/s Patel Engineering, SEW and Coastal Projects Limited (CPL), signed

“We have exciting plans to expand our investment in India to meet the demand in India's booming infrastructure market.”

Kazuhiro Fukumoto General Manager, Sakai Factory, Hitachi Zosen

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Robbins is working with lead India construction company Jaiprakash to ensure success of the longest, largest diameter, hard rock TBM tunnel in India's history and claimed by Robbins as the longest in the world without intermediate access points.

a contract with Robbins for the supply of a 10.0 m (32.8 ft) diameter EPB, as well as the back-up system, cutting tools, spares and continuous conveyor system. CPL also opted for Onsite First Time Assembly (OFTA) of the machine at the jobsite, in order to expedite the project schedule. The Robbins hybrid machine is a fully functional hard rock Single Shield and soft ground EPB TBM, designed for long sections of 180 MPa (26,000 psi) UCS jointed rock and marble, interspersed with clay and gravel. In sections of soft ground, the machine runs as a standard, pressurized EPB with an abrasion-resistant, shafttype screw conveyor. When short sections of rock or mixed ground are encountered, the machine can be run in non-pressurized EPB mode. In longer sections of rock, the TBM can be converted to a hard rock Single Shield setup by switching out the screw conveyor with a belt conveyor. The hybrid EPB was completed using Onsite First Time Assembly (OFTA) in Madhya Pradesh, India on March 14, 2011. East West Gas Pipeline (Tunnel Length: 100m; Diameter: 1524 m) The pipeline is planned to transfer


30 billion cubic meters of gas from the gas fields off India's east coast (Kakinada, Andhra Pradesh) to the refineries located in the west (Ahmedabad, Gujarat). Two Herrenknecht Hard Rock Single Shield TBMs were used since 2006 during the construction of the pipeline. The machines crossed roads and railway tracks along their tunnel route. With minimum covers of only 1.5 meters 60-inch steel pipes were pushed through the underground using the pipe jacking method. The two machines M-1118M and M-1120M with hard rock cutterheads and electric drives were optimally equipped for operating in the hard and partially brittle rock formations. The system for the transport of the excavated material was quickly operational comprising belt conveyors, muck skips and winches. Ghatkopar High Level Tunnel The project comprises a 2.6-km long trenchless tunnel. Tunnelling challenges include massive and weathered basalt as well as the groundwater level along the tunnel alignment. A Herrenknecht TBM2500XH, equipped with 21 discs, is deployed to crack the basalt. The tail seal of the

Rockster India Ltd


TBM avoids groundwater ingress during ring installation. Water ingress through the cutting wheel of the micromachine is pumped out. Varavalli Reservoir Two Gripper TBMs with a diameter

of 3,000mm drove several freshwater tunnels in Mumbai's northeastern suburbs. Since rock strengths of up to 250MPa had to be mastered along the overall 9.7 kilometer-long tunnel sections, two Herrenknecht Gripper TBMs were used. With diameters of 3.0

and 2.8 meters, they are the smallest Gripper TBMs ever designed and manufactured by Herrenknecht. Bangalore Metro Two 6.44 diameter Hitachi Zosen Slurry Tunnel Boring Machine (TBM) were used for this tunneling project. The tunneling geological profile was a mixture of soil and bed rock, which required a Slurry Type of TBM machine equipped with 1200kW cutter head drive power, a First machine of this type in India, to meet such challenge. Kishanganga Hydroelectric Project The tunneling geological profile was a mixture of basalt, andesite, granite/granodiorite. SELI was involved in the supply of a new Double Shield Universal TBM, back-up system and auxiliary equipment (rolling stock, ventilation system, spare parts etc.). The project involved excavation of the Headrace Tunnel of 14,630 m by double shield TBM having boring diameter of 6,10 m, internal finished diameter 5,20 m. Tunnel lining with concrete segments. Future Outlook The TBM industry is subject to a continuous improvement process with the future trending towards larger tunnel profiles, long tunnel drives, tunnels at greater depths and with high groundwater pressures, which have in the past not been seriously considered feasible. Demanding project requirements under grueling conditions and innovative ideas of contractors and planners are driving further technological development in TBM technology. Improved safety requirements and comprehensive risk management are also playing an increasingly important role for all parties involved in the design and execution of construction projects with today's tunnels are passing beneath densely-populated areas, mountain ranges or rivers and estuaries. Picture Source

Herrenknecht Hard Rock TBM used during the 2006 construction of the East-West gas pipeline

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www.robbinstbm.com, AP / Keystone / Batzarini www.skyscraper.talkwhat.com www.herrenknecht.com

Roshanlal Jain & Sons (Roljack Industries)

Tunnel Engineering Repair & Rehabilitation

Tunnel Repair and Rehabilitation Using Shotcrete Special Correspondent

T

he art of rehabilitation of tunnels has flourished and developed significantly over the last couple of decades. Several hundred railroad, highway, and conveyance tunnels have been successfully rehabilitated, converted, and/or enlarged. Much of this development can be attributed to the successful use of steel fiber reinforced shotcrete. One of the major attributes of shotcrete is excellent bond to the substrate, usually superior to the bond achieved with cast-in-place concrete. This has made shotcrete particularly well-suited for repair

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and or rehabilitation work of vertical and overhead surfaces. The flexibility and adaptable nature of steel-fiber microsilica shotcrete is ideal for rehabilitation of tunnels. Many developments in shotcrete technology during the 1980s have enhanced shotcreting capabilities. These include advances in shotcreting materials technology and improved methods for batching, mixing, supply, and application. The developments have stemmed largely from the desire of engineers and contractors to improve the quality and durability of inplace shotcrete, increase View of a shotcrete operation. Look closely and you can see the stream of wet concrete being blasted onto the rock surface Pic courtesy: http://thelaunchbox.blogspot.in


shotcreting productivity and economy, and expand the range of shotcrete applications. It is because of these developments in shotcrete technology, enlargement and rehabilitation of tunnels without fully taking the tunnel out of service is not only technically but also economically feasible considering the cost of other alternatives Enlargement was usually accomplished by raising the crown but some have been enlarged by lowering the invert, which is much more difficult and time-consuming. Harvey Parker & Associates, Inc., in Bellevue, WA have rehabilitated several tunnels that were over a century old, allowing these tunnels to begin their second century of service. This long life represents a huge life-cycle benefit for the tunnel owner, and this cost advantage can be maintained by conducting an occasional rehabilitation from time to time. The increase in the number and type of tunnels being rehabilitated over the last few decades was largely made possible by the continued development of ground support methods using rock bolts and steel fiberreinforced shotcrete. Repair and Rehabilitation is done for several reasons. Sometimes rehabilitation work is done simply to extend life or to improve future performance, such as reduction of maintenance or to improve safety. Generally, highway tunnels, such as the one illustrated in Fig. 1, fall into this category. Other reasons for rehabilitation include: 1) enlarge the tunnel to increase clearances or capacity or 2) change the type of tunnel from one use to another. On the other hand tunnel gets damaged because of following reasons needing urgent repair to bring back the traffic into operation through it again, these are: 1) Damage due to lack of maintenance, 2) Damage due to fire, 3) Damage due to natural calamity such as earth quake, 4) Damages due to unexpected operational problems. Examples of damage occurring due to reason 4 are shown in Fig. 2. The introduction of double-stack container cars and other special or extra-large cars (for example, tri-level auto racks) created a need for enlargement of most of the tunnels in the United States and Canada. This is an ideal example of

Figure 1: Shotcreting for rehabilitation of highway tunnel.

tunnel rehabilitation to satisfy a need for larger tunnels and better service rather than just to extend their lives. Many of the railroad tunnels in the west and several on the east coast have been enlarged by increasing clearance in the crown. Clearances were improved mostly by crown mining, which consisted of either cutting a notch in the existing lining or rock walls, as shown in Fig. 3, or by

Fig. 2. Some failed tunnels at Jiulongkou Coal Mine.

Figure 3: Tunnel clearance notch in a railroad tunnel.

complete or substantial removal of the brick or concrete lining. Importance of fast recovery of the Tunnel for uninterrupted service:Tunnels are vital to keeping our transportation systems going, and interruptions of service are rarely permitted. Rehabilitation that requires invert work usually shuts the entire tunnel down. It is better to concentrate tunnel rehabilitation on the crown and sidewalls if at all possible. Typically, there are no alternate routes so tunnel work must be done with the least disruptive effect on paying traffic. This is done by either temporarily shutting down one lane or one track in multiple lane/track tunnels or by managing traffic to permit work windows that might last from 1 to 8 h. Yes, work can be accomplished in windows of 1 or 2 h; it is not very efficient but sometimes that is all the time one can


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get in any one work window. Rehabilitation work while keeping the tunnel in service requires enormous planning, coordination, and selection of proper construction methods. Advances in Shotcrete Materials for Tunnel Repair/ Rehabilitation job Before the 1980s, most shotcrete used for repair and rehabilitation in North America was made of conventional portland cement and sand mixtures applied by the drymix shotcrete process. Some polymer- modified shotcrete was used for remedial work in aggressive exposure conditions. There also was limited use of wet-mix shotcrete, primarily for large- volume projects. Today, both dry- and wet- mix shotcretes often contain supplementary cementing materials, such as fly ash and silica fume, as additions or partial cement replacements. These materials improve shotcrete workability and performance. In the early 1970s, a major advance in shotcrete technology was the development of steel-fiber- reinforced shotcrete (SFRS). SFRS is particularly useful for remedial applications in aggressive chemical or marine environments because it resists corrosion better than shotcrete with conventional steel reinforcement. As long as the shotcrete matrix retains its inherent alkalinity and remains uncracked, deterioration of SFRS is unlikely. Corrosion of the discreet steel fibers occurs only to the depth of surface carbonation in the shotcrete. If corrosion of the surface fibers is aesthetically objectionable, a flash coat of plain, unreinforced shotcrete can be applied. SFRS has another advantage: It's more user friendly and less prone to problems caused by inadequate workmanship. For example, it eliminates the shadowing and voiding problems sometimes encountered in conventionally reinforced shotcrete repairs (Refer Fig. 4).

Fig. 4. An extreme example of shotcrete improperly applied to mesh reinforcement shows build-up of shotcrete on the face of the mesh and shadowing and voids behind.

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Steel-fiber reinforcement addition rates vary from about 60 to 140 pounds per cubic yard, depending on job requirements and fiber type and size. Generally, higher fiber addition rates are used in structures subject to severe stresses and strains imposed by: -

Impact or explosive forces. Heavy, repeated, dynamic cyclic loading. Large exposed surfaces, which are more susceptible to shrinkage cracking

Advantages of Steel Fiber Reinforced Shotcrete Steel fiber-reinforced shotcrete offers the flexibility needed to adapt to rapidly changing ground conditions and uncertain work window schedules. In some projects, due to the remote location, a concrete batching plant is not available. Shotcrete dry mix including steel fibers and microsilica can be purchased in prepackaged 1 y3 (0.75 m3) bags (sling bags) and conveniently stored at the site until needed (refer to Fig. 5,6,7). Usually the dry mix is batched at a centrally located plant where the quality of the shotcrete mixture can be controlled before shipping to the site. Shotcrete from sling bags can be placed by the dry or wet method. When placing steel fiber-reinforced shotcrete in tunnels, costly steel or wood arch forms, and even rebar or mesh, are not required. Time is not wasted while erecting, curing, and removing forms or hassling with mesh. Shotcrete will conform to the rock surface and smooth out the irregularities caused by blasting. In cases where the tunnel rock is locally unstable, the design ground support can be increased to carry the unbalanced load. Additional shotcrete and rock bolts are placed as necessary to stop movements as documented by monitoring. Shotcrete can be finished with a trowel to a smooth surface equivalent to a form finish. In a pedestrian tunnel, shotcrete was placed in the steel reinforced arch of the horseshoe-shaped tunnel and elegantly finished to a smooth surface. In tunnel sidewalls, the presence of steel

Fig. 5: Shipment of prepackaged Shotcrete in 2205 lb (1 metric tonne) bags to an underground mine


strength of these mixtures exceeds 5000 psi (34.5 MPa) in 28 days. The fiber content can be adjusted higher or lower as necessary to accommodate the ground conditions. How Rehabilitation is done Keeping Tunnel in Service Rehabilitation work while keeping the tunnel in service requires enormous planning, coordination, and selection of proper construction methods. The flexibility of shotcrete,

Fig. 6: Shotcrete storage area at Falconbridge Raglan property

Figure 9: Railroad tunnel clearance excavation: single to double track

Fig. 7: Sling bags of shotcrete mixture and work train at a railroad siding

fibers on the surface could cause scratches on the arms of pedestrians. In these situations, the last 2 in. (5 cm) of shotcrete are placed without steel fibers. Typical shotcrete specifications for mixture proportioning indicate that each cubic yard contains a minimum of seven and a half sacks of cement (420 kg/m3), 80 to 100 lb (50 to 60 kg/m3) of steel fiber, 80 lb (50 kg/m3) of microsilica, and a coarse aggregate/total aggregate ratio of 0.4. The compressive

especially with volumetric mixing, is extremely valuable to tunnel rehabilitation. Usually, all work is done from work platforms designed specifically to make all the work (including handling muck and rebound) done as efficiently as possible. A schematic of a special work train that is used for railroad tunnel rehabilitation is shown in Fig. 8. Examples of Tunnel Rehabiltation Using Shotcrete -

A railroad tunnel in the eastern United States was enlarged from a single-track tunnel to a twin-track tunnel. Originally lined with brick, the tunnel was taken

Fig.8. Typical Railroad Work Train (Schematic Diagram)


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Fig. 10. Restoration Procedure

out of service and enlarged to obtain the double-track clearance. The new liner consisted of steel fiberreinforced shotcrete and rock bolts. Shotcrete thickness varied from 4 to 12 in. (10 to 30 cm). Typical rock bolt lengths were 12 ft (3.7 m) but in places ranged up to 18 ft (5.5 m) long. Figure 9 shows the excavation process and the shotcrete liner. The tunnel encountered open abandoned coal mine works, and the flexibility of utilizing shotcrete and tensioned rock bolts was invaluable in advancing the work through difficult ground. -

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A highway tunnel on the west coast was rehabilitated because of the limited clearance and continued deterioration of the timber lining. The liner consisting of timber sets and lagging was replaced with 4 to 5 in. (10 to 13 cm) of steel fiber reinforced shotcrete in the arch and 2 to 4 in. (5 to 10 cm) of concrete on the sidewalls. Rock dowels anchored with epoxy resin cartridges were installed after an initial layer of shotcrete was installed. Repair of a deep-mine permanent access tunnel using bolt, mesh and shotcrete Jiulongkou Coal Mine, China). Shotcrete prevents the failed rock mass from falling and further weathering. The total thickness of shotcrete applied was 120 mm on average and was sprayed as three layers. The first and second layers together were 70 mm in thickness. This allows the dilatancy deformation to be released. Sometimes there were local failures in the first and second layers. The final layer was 50 mm in thickness and was sprayed after the surrounding rock mass deformation became stable. Steel mesh was used together with shotcrete to increase the tensile and bending strengths of the shotcrete. Steel wire with a diameter of 6.5 mm was selected to form a 125x125-mm2 mesh. Application of rock bolt, steel mesh and shotcrete to repair seriously deformed tunnels of the Jiulongkou deep coal mine shows that the support approach and techniques based on the loosening zone concept were very much successful.


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Restoration of a Tunnel Damaged by Noto Offshore Earthquake in coast of Suzu city in Japan in 1993 was carried out using steel-fiber-reinforced shotcrete (SFRS). Spray of steel-fiber-reinforced shotcrete was adopted because it was considered to increase bending tensile strength and ductility under uncertain additional loads from the ground loosened under the influence of the earthquake. The SFRS design thickness was 150 mm and mean extra thickness provided was 50 mm. The restoration procedure is shown in Fig. 10.

Conclusion In the 80 years since the shotcrete process was developed, shotcrete has played a valuable role in repair and rehabilitation projects. One of its major attributes is excellent bond to the substrate, usually superior to the bond achieved with cast-in-place concrete. This has made shotcrete particularly well-suited for repair of vertical and overhead surfaces. The use of steel fiber-reinforced shotcrete made the rehabilitation of railroad and highway tunnels practical and economically viable. The strength and durability of steel fiber microsilica shotcrete in combination with tensioned or untensioned anchor bolts can handle almost any type of tunnel ground loading. Shotcrete can be installed utilizing the wet or dry methods and can be installed to sculpt any tunnel shape without the use of costly forms or the need for rebars or mesh. However advanced research is still going with with other varieties of shotcretes with polypropylene fibers and other polymers. Reference -

H.W. Song, S.M. Lu, Tunnelling and Underground Space Technology 16 (2001), pg. 235-240.

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M. Kunita, R. Takemata and Y. Lai, Tunneling and Underground Space Technology, Vol. 9, No. 4, pp. 439-448, 1994.

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The are of Tunnel rehabilitation with shotcrete, Harvey Parker et al.

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Eugenkleen MC - Bauchemie Mueller GmbH and Co. KG

O

ver the past decade, the use of concrete admixtures, especially plasticizers and superplasticizers, is showing upward trend in India. The advent of concrete pumps and transit mixers has also contributed to this, as the use of superplasticizers enables trouble-free pumping operations and minimizes pipe blockages. With the advent of Major Metro Projects across India, durability of concrete used especially for tunneling segments is of prime importance. The earlier attitude of taking recourse to the use of admixtures only after facing problems is changing fast, and now, in most tuneling projects, high performing admixtures are already included in the specifications and the mix is designed to achieve the necessary properties. The concrete for tunnel segments necessitates the concrete to have the following properties: -

Compressive strength Workability Surface Finish Durability

As part of the durability requirements, concrete is or should be generally tested for the following properties: -

Chloride migration

-

Sulfate resistance Water absorption Acid resistance Porosity Freeze Thaw Resistance

This can be achieved using the latest technologies available for concrete. Concrete is now no longer a material consisting of cement, aggregates, water and admixtures but it is an engineered material with several new constituents like PFA, GGBSF, Microsilica, Metakaolin,

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Colloidal Silica and several other Binders, Fillers and Pozzolanic materials. The concrete today can take care of any specific requirements under most exposure conditions. The mix designs are getting relatively complex on account of interaction of several materials and mix design calls for expertise in concrete technology and materials. High Performance Concretes will have to be adopted for tunneling segments, considering special properties as well as low cost maintenance strategies. What type of Concrete do we use? Concrete used in tunneling applications need the following outstanding properties viz. Compressive Strength, High Workability, Enhanced Resistances to Chemical or Mechanical Stresses, Lower Permeability, Durability etc.This will necessitate the useof High Performance Concrete. SomeHPC types which will hold the key for tunneling applications, can be classified into: -

Self Compacting Concrete / High workability concrete Concretes resistant against aggressive media

1. Self-Compacting Concrete (SCC) Self-Compacting or Consolidating Concrete (SCC) as the name signifies should be able to compact itself by its selfweight under gravity without any additional vibrations or compaction. Self Compacting Concrete should be able to assume any complicated formwork shapes without cavities and entrapment of air. The reinforcement should be effectively covered and the aggregates should be fully soaked in the concrete matrix. In addition, the concrete should be self-leveling type and self-defoaming without any external compaction. Figure 1shows SCC. The formulation of Self Compacting Concrete has the latest


concrete technology and it requires in-depth knowledge of materials and meticulous testing procedures before the concrete is designated as Self Compacting Concrete (SCC).Self Compacting Concrete has the following special advantages. -

Saving of costs on machinery, energy and personnel for vibrating the concrete Considerable improvements to exposed surfaces (Fair Faced Concrete), less efflorescence. Marked improvements in durability on account of better compaction Extremely suitable for slim and complicated moulds Covers reinforcement effectively. Better adhesion between cement binder and aggregates. Reduction in demoulding time Advantage with respect to sound pollution

the essential concrete properties a high-performance PCE (polycarboxylate ether) needs to be incorporated in the mix. By adjusting the particle size distribution on a micro scale the permeability of the concrete is reduced which minimizes the penetration of aggressive substances. Depending on the degree of dispersion these material particles more or less completely fill the spaces between the cement particles. During hydration the pozzolanic silica reacts with the free calcium hydroxide to form calcium silicate hydrates. This gives a denser concrete structure.

Figure 2a: Densest packing grading curve

The main materials, which can help change normal concrete to durable aggressive media resistant concrete, are: Figure 1: Flow of Self Compacting Concrete around reinforcement

Therefore while calculating the costing and economics of Self Compacting Concrete all the above mentioned advantages should be converted to cost parameters. This kind of concrete can give advantage of good Compressive Strength, workability and finish to the tunnel segments and may prove suitable.

New Generation PCE Based Admixtures Condensed Silica Fume or Microsilica Slurry or Latest Generation Aluminosilicates

a. PCE Based Admixtures: Most of the new generation superplasticizers are from the Acrylic Polymer (AP) family. Polycarboxylate is a common term for the substances that are specifically used as Polyacrylate or Polycarboxylate ethers (PCE). The PCE based Super Plasticizers are by far superior to the conventional ones with respect to initial slump as well as slump retention with time. The efficient working of these plasticizers is due to the new type of

2. Durable Concrete resistant against aggressive media One major application of HPC is to increase the durability of concrete where aggressive underground conditions are anticipated. This can be achieved physically by resorting to very dense aggregate packing. The packing curve is shown in Figures 2a and 2b. This is practically possible by selecting a very smooth sieve line from largest aggregate to the smallest grain of Mineral Additives like Microsilica or New Generation Aluminosilicate slurries. Chemically, cement by itself is not acid resistant. The acid resistant binder is formed by combination of cement, microsilica / aluminosilicate and flyash.To control permeability very low water cement ratio has to be adopted. So as to provide

Figure 2b: Pictorial representation of Densest packing of aggregates in Concrete


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molecule designs. PCE based superplasticizers produce excellent properties when used with cementitious materials. The disadvantages associated with longer setting times of conventional superplasticizers is offset by PCE based super plasticizer and therefore its use in concrete can also attain high early strengths.Figure 3 shows the structure of PCE molecule and its working mechanism - steric hindrance. The development of highly effective superplasticizers with long and consistent duration of action is therefore an important precondition for the production durable concrete, due to low water contents and high early strength requirements.

Figure 4: Workability Comparison of MSF/NSF against PCE at lower dosage

Arc Furnaces used in manufacture of Silicon, Ferrosilicon and other alloys of silicon. There are three main reasons for the incorporation of Silica Fume as an additive for HPC. Microsilica has a filler effect i.e very fine particle distribute itself in the space between the materials in the concrete in a homogenous way to give rise to more dense concrete. Silica Fume improves the strength of the transition zone between cement paste and aggregates. CSF is highly pozzolanic in combination with Portland cement. Figure 6 shows structure and effect of Microsilica.

The advantages of these New Generation polymers are very clear, not only in terms of performance but also in terms of the dosages used for similar conditions and this factor balances the disadvantages in economy, as New Generation Superplasticizers are relatively expensive per unit price.Figure 4shows workability comparisons of MSF/ SNF against PCE. Figure 5 shows comparative development of compressive strengths and the dosages required are very low.

During cement hydration there is surplus of Calcium Hydroxide. The Added Condensed Silica Fume's SiO2 reacts with surplus of Calcium Hydroxide. This results in greater amounts of Calcium Silicate Hydrate, which are denser and stronger than Calcium Hydroxide. The pozzolanic reaction and the filler-effect lead to a compaction of the cement paste and the conversion of CH crystals into CSH gel leads to a homogeneous paste. This phenomenon of dense packing in the interface zone of aggregates also contributes to increase in strength of the concrete on account of aggregates fully contributing their strength to the set concrete. Therefore the high strength of concrete with silica fume is greater than those of the matrix, indicating the contribution of the aggregate to the total strength.Experience shows that slurry forms of Microsilica (50:50 with water) have all the benefits in transportation, dispensing methods, mixing times and dispersions to get the desired effect in durable concrete for tunneling segments.

b. Condensed Silica Fume / Microsilica:The term "Microsilica" is adopted to characterize the silica fume, which is used for the production of concrete. Microsilica or Condensed Silica Fume (CSF) is a by-product resulting from reduction of high purity quartz with coal in the Electric

3. New Generation Aluminosilicates:New generation aluminosilicates based on special nano-crystallizers have been developed. These new materials improve the properties that are crucial for the durability of highperformance concrete. In addition to reducing chloride

Figure 3: Structure of PCE Molecule and its Mechanism of action

Concrete additives based on PCE offer advantages like: -

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Significant reduction of the water demand of the mix Little loss of consistency Short setting times High early strengths Low tendency to segregation


Credence Engineers Pvt. Ltd

JB Engineering and Industrial Company


of the concrete surface.Aluminosilicates performs over the some of the disadvantages of Microsilica: -

Graded for dispersion in concrete Graded particle size Optimizes mixing time within concrete Good dispersion reduces unreacted material in the mix and increases passivation by C-S-H gel on aggregate surface Microsilica

Aluminosilicates

By-product of the Ferrosilicium- & Manufactured product, it is only Silicium production, not specifically produced for use as concrete additive produced for concrete Quantities are depending on the Quantities are not depending on other metal industry and the economic industries and are unlimited, the development reforereliable availability Quality of the product has a higher High quality standards for end deviation because it is only a by product because every step in product production is controlled

Figure 5: Strength Comparison of PCE versus MFS/NFS at lower dosage

Table 2: Key Difference Between Microsilica and Aluminosilicates

Figure 6: Structure and Microfiller effect of Microsilica in Concrete

migration, an exceptional chemical and resistance to aggressive media of the concrete can be achieved with Aluminosilicates. The concrete structure is simultaneously reinforced right down to nanoscale, density is improved and compressive and flexural strength as well as abrasion resistance of the high-performance concrete is increased. There is also a significant reduction of micro-crack formation,which makes it particularly suitable for the production of tunneling concrete. Aluminosilicates reduce the proportion of portlandite by way of a pozzolanic reaction that changes it into the aluminosilicate crystals into calcium silicate hydrate. In addition to the unique resistance against acids a crystalline micro-reinforcement within the concrete structure is achieved. This reduces the risk of micro-crack formation, rendering concrete impermeable. Due to high homogeneity and reduced tackiness compared with microsilica-basedconcrete, workability is improved significantly. In many instances this enables the production of high-performance concrete that can be pumped. In addition, a distinct improvement of the building structure's aesthetics is gained due to the fair appearance

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Figure 7: Comparison of Strength Development between Microsilica and Aluminosilicates

-

Material if agglomerated improve strength of the mix Reduces risk of Alkali Silica Reaction by Agglomeration of aluminosilicate particles

Table 2 shows some of the key differences between Microsilica and Aluminosilicate slurries. Figure 7 shows the comparison of strength development between Microsilica and Aluminosilicates. All in all the use of PCE Admixtures and Microsilica or Aluminosilicate Slurries in addition to the standard ingredients in concrete, plus excellent mix-design practices can facilitate the production of high performance concretes resistant to aggressive media, suitable for use in tunneling applications.

IBK Media

Construction Chemicals

Construction Chemicals Industry in India

'vision 2020' Dr. SK Manjrekar

Chairman & Managing Director

Ms. Ishita Manjrekar Sr. Associate Sunanda Specialty Coatings Pvt. ltd.

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he Indian construction chemicals industry is growing at a healthy pace of 14-15% CAGR due to the huge emphasis on infrastructure across the country. The demand for construction chemicals is dependent on the construction industry and with an increased focus on sustainability and green buildings, construction chemicals are assuming a significant role. Indeed, it is no surprise that it is being referred to as a “sunrise industry”. Glaring Facts of the Indian Construction Chemicals Industry Construction chemicals play a vital role in concrete performance. India being the second largest manufacturers of cement in the world should by default be the second largest consumers of construction chemicals. In developed countries, construction chemicals are used in every 200/cu.m of concrete and this is inadequate for producing about 2% of global production. However, the Indian construction chemicals industry is a mere INR 2500 crores per annum! If one considers the quantum of Indian cement production, the construction chemical industry in India should be INR 20,000 crores/ USD 4 billion market vis-à-vis the current figure of INR 2500 crores/USD 500 million ! Challenges and Critical Change Agents Despite holding such staggering potential, growth by default for this industry may not be easy even with the construction sector having more than 50% outlay of every five year plan as well as being second largest cement manufacturer! Factors like limited awareness, lack of awareness, conventional construction practices/ malpractices remain huge bottlenecks for the industry. And if the construction chemical industry does grow, whether the industry will

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create sustainable and durable structures, will it bring about reduction in carbon foot print, will it bring changes in environmental conditions these are critical questions that have to be answered. There is no doubt that the growth of construction chemical industry is imperative or else consequences will be far reaching disastrous. However, stop gap measures like seminars and discussions limited to a few sections or few persons of the industry is not sufficient. It requires a well-drawn, meticulous, long term plan VISION 2020 for the Indian Construction Chemical Industry! In the last four decades, there have been several developments in the Indian cement industry - India has grown from 33 million tons to 330 million tons of cement/annum. It ranks 2nd in cement production. We have transitioned from 33 GRADE cement to 53 GRADE cement and from 1:2:4 era to mix design era (though mainly in metropolises) on a percentage basis. While speed of the work remains critical due to economic consequences, qualitative aspects are at times on sacrificial altars either by compulsion or out of ignorance. But the industry has gradually awakened to the significance and criticality of the role played by an inexpensive, ignored and yet avoidable “nut and bolt” in the huge gamut of the construction machine “construction chemicals”. There are still large sections in the construction and engineering fraternity that are not fully aware of the importance and benefits of construction chemicals. Sadly, chemistry of cement hydration and concrete as material are not included as part of syllabus in engineering colleges and universities. There have been a few knowledgeable and experienced people who have made an effort to spread awareness about the subject. Indian personnel/ engineers exposed to construction chemicals in other countries like the Middle East have brought back their knowledge and information and applied it locally.

This has helped in gaining acceptance to the concept of construction chemicals which was hitherto considered superfluous. The entry of foreign market players, capitalizing on the market potential of the country, has also raised the bar. High real estate prices have led to increased activity in repairs and rehabilitation and this has led to increased usage of construction chemicals in cities like Mumbai. Lack of structured training, professional practice or client training and passive and under educated prescription in use of construction chemicals in organized sector s like government departments has led to mushrooming of street smart players the unorganized sector. These players have capitalized on the marginal specifications and usages from all and sundry but a positive side effect of this phenomenon has been a raised awareness of the indispensability of construction chemical. VISION 2020 - Objectives and Actionables As always the quality, consistency, desire to be knowledge partners, transparency, performance based specifications and above all being part of global explosion of knowledge has to once again prevail and all concerned have to become more discernible, informed, proactive and customer friendly. Hence, this is the ideal time to make a vision statement A VISION 2020 for the Indian construction chemical industry. This calls for collaborated efforts involving all stakeholders the industry, the end users, the concerned ministry, concerned approved organization in chemicals like FICCI, codal organizers like BIS, Expenditure on Admixtures per cubic meter

United States

USD 4.5 per cu.m

China

USD 2 per cu.m

India

USD 1 per cu.m

The construction chemical industry in India accounts for only 0.4% of the total construction spendinstead of 1% of total construction spend which is the norm in developed economies! Picture courtesy: http://marshmucking.blogspot.in


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World market for construction chemicals (US$ millions) 2009

2014

North America

4,684

5,650

Central and South America

1,815

2,317

Western Europe

6,557

7,577

Central and Eastern Europe

988

1,186

Middle East and Africa

1,827

2,399

Japan

3,560

3,578

China

7,868

12,106

Despite being the second largest consumer of cement in the world, India does not figure significantly in the world market for construction chemicals!

university syllabi committees and even Planning Commission to collaborate and recognize the importance of this industry. The aim of such collaboration should be 'to make a vision statement and strive to accomplish the objectives with the help of all the stake holders'. The VISION 2020 should aim at the following. 1. To make construction chemical industry a major partner in the construction segment of the country. 2. To increase the use of construction chemicals to more than 100% year on year. 3. Make construction chemical industry fully organized sector. 4. Establish an association of the industry players which will be having linkages with concerned government departments, ministries and the industry. 5. Spread awareness and abolish the myths about unavoidable use of construction chemicals to make durable and sustainable construction. 6. Establish neutral laboratories which will test the 'uniformity and performance based parameters' of various construction chemicals without bias in order to establish and instill the confidence in customers' minds and also to bring the 'system' to the approach of construction chemicals industry. 7. Evolve various standards for the range of construction chemicals, matching international standards likeACI, JIS, DIN, ASTM etc. in

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collaboration withBIS 8. Train and assimilate unorganized sector in the main stream of activities. 9. Grant a status of “chemical industry” to this sector so that prevailing rates of various taxations can become applicable, thus making the pricing structure competitive. 10. Create focus on sustainability and durability by liaising with government authorities to offer incentives till a threshold / cut off year -say 2020 11. By 2020 achieve minimum `20,000 crores (USD 4 billion) production and ` 40,000 crores (USD 8 billion) 12. Members of the industry should engage in continuous innovation, based on the conditions of Indian subcontinent as well as training the personnel / applicators on regular basis. 13. Create trained /educated distribution network, which is important final link with the customer. Introduce the subjects of concrete, corrosion and construction chemicals in the syllabus of all the universities conducting civil engineering related programs. These are just some points to ponder in “VISION 2020”. Many more can be added with the help of wider debate throughout the industry. This VISION 2020 will identify that this is not merely 'sunshine industry' but it will take the sustainability and durability concerns of India in “sunshine zone”. The Indian construction chemicals industry is in a desperate need for a wakeup call. While it has lurched forward


with the impetus in infrastructure, the growth by default mode may create complacency. Quick fixesare not enough. The industry is at its critical inflexion point and in urgent need of boldness and a fresh vision. The VISION 2020 will sound the siren but it is the persistent, coordinated efforts of the stakeholders - the construction chemical players, builders and contractors, academicians, the government and engineers - who can create the magical alchemy. Author's Bio DR. S. K. Manjrekar obtained his Ph.D. in 1977 from University of Bombay in Corrosion and Material Science and has long experience of 32 years in the field of Construction Chemicals and concrete related materials. He is the past president of ACI-India Chapter from 1998 - 2001, 2001 2003, and 2005 - 2008. He is one of the two members in India to have been conferred upon with the Fellowship of American Concrete Institute in 2000 in San Diego, USA. He has been conferred by ACI (International) 'Chapter Activities Award' in 2003 in Vancouver Canada for his dedicated service to the ACI India Chapter and years of service to the concrete industry. Dr. Manjrekar has published more than 200 papers in various national and international journals that have resulted in deeper understanding of concrete and construction chemicals. He is a visiting faculty at engineering colleges like VJTI, IIT Mumbai, NCN Chennai, Central University of Rajasthan and many other institutions across the country. He has delivered many invited lectures and keynote addresses on cement and concrete as a material, polymers admixtures and their applications, corrosion protection, waterproofing etc in civil engineering field all over India and countries like Dubai, Qatar, Kuwait, Egypt, Romania, Hong Kong, U.K., USA etc. He has been invited to Kuwait to give key note speech in the conference “Kuwait Cement & Concrete” held on 08th 09th June 2010 and earlier in 2007. Dr. Manjrekar is also the Chairman and Managing Director of M/s. Sunanda Speciality Coatings Pvt. Ltd., Mumbai manufacturers of entire range of construction chemicals who also offer consulting services in related field for its use for last 3 decades.

MM Castings (P) Ltd

Infrastructure Tunnels

The Gotthard Tunnel Pass: A True Tunneling Marvel Bhavani Balakrishna

W

ith a planned length of 57 km and a total of 153.5 of tunnels, shafts and passages planned, the Gotthard Base Tunnel will become the longest tunnel in the world once it gets completed in the year 2017. The route over Gotthard Pass or one of its tunnels is one of the most important passages through the Alps on the north-south axis in Europe. Traffic has increased more than tenfold since 1980 and the existing road and rail tunnels are at their limits. In order to provide a faster and flatter passage through the Swiss Alps, the Gotthard base tunnel was planned cutting through the Gotthard massif. The tunnel that courses some 2000 meters below the rock and lies only about 550 meters

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above sea level will strengthen shift of transalpine transit traffic from road to rail and is part of NRLA (New Rail Link through the Alps) initiated by the Swiss authorities with the Lötschberg Tunnel, inaugurated in 2007. Once completed, it will carry freight loads of up to 4000 tonnes, 200-250 trains per day in each direction travelling at up to 250kmph. The Gotthard Base Tunnel consists of two 57-kilometres-long single-track tubes. The two rail tunnels are about 40 meters apart and joined approximately every 325 meters by connecting galleries. Two multifunction stations are located in the sections, Faido and Sedrun, to allow trains to change from one tunnel to the other, complicated tunnel and adit systems due to the requirements


of construction, emergency, ventilation and technical niches. For construction purposes, the Gotthard Base Tunnel was divided into five separate sections of different length - Erstfeld, Amsteg, Sedrun, Faido and Bodio. The construction of the tunnel has involved primarily the use of tunnel boring machines apart from drilling and blasting for the two stations as well as the section of the main tunnel in Sedrun due to expected bad geology in Sedrun. Of the around 152-kilometreslong tunnel system of the Gotthard Base Tunnel, including all passages and shafts, around 56 % were excavated by tunnel boring machine and around 44 % by drilling and blasting. During the excavations, a total of more than 28


1500 on 20 kilometers and more than 2000 meters on approximately 5 kilometers. The Faido-Sedrun section is reporting the maximum overburden of about 2400 meters. The geologists predicted that in the Amsteg section both tunnels would encounter the constructionally extremely unfavourable Intschi zone along a length of several hundred metres. Through the entire Intschi zone an average daily advance rate of 6 metres was expected. In the fault zone itself, the construction schedule even foresaw an interruption in driving of four months to allow measures for stabilizing the rock conditions. These measures turned out to be unnecessary. The planned stoppage of the two tunnel boring machines was not required. In the northern part of the Tavetsch

intermediate massif around Sedrun excavated spaces have the tendency to close again unless countermeasures are taken. This phenomenon is known as "squeezing rock". To hold the excavated cross-section open, supporting means have to be used. If after excavation a certain amount of deformation is allowed, the force needed to hold the space open can be substantially reduced. To counter the immense rock pressure, new methods of tunnel construction were used at Sedrun. To provide support for keeping the excavated cross-section open, deformable steel rings were inserted which gradually close under the pressure of the squeezing rock until their maximum supporting force is attained. Each arch consists of eight segments which are joined together by slightly yielding

Altdorf

Erstfeld

Erstfeld length 7.4 km

Amsteg Amsteg length 11.4 km

Sedrun

million metric tons of rock were transported out from under the mountains. From north to south, the 57 kilometers long Gotthard Base Tunnel passes through crystalline rock sections, including the Aare massif to the north, the Gotthard massif and the Penine gneiss zone to the south. The massifs consist of high-strength igneous and metamorphic rock and are intersected by narrow sedimentary tectonic zones. The main geological risks predicted were rock bursts, rock wedge instabilities and water inflow. A great part of the tunnel will be situated underneath a considerably high overburden: more than 1000 meters of overburden on a distance of approximately 30 kilometers of the tunnel, more than

Sedrun length 6.8 km

Gotthard Base Tunnel length 57 km

Faido length 14.6 km

Faido Bodio length 16.6 km

Open Tunnel line Gotthard Base Tunnel Postponed Existing railway line Shaft, adit Exploratory bores piora syncline The old and now new Gotthard Railway line.

Bodio Biasca

Picture Courtesy: www.tu-freiberg.de


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connectors to form two concentric rings. Under the pressure of the rock, the rings are slowly pushed together until the maximum supporting force is reached. Although this technology was already known from German coal mines, it had never before been applied in these dimensions in tunnel construction. The selected concept with deformable steel inserts more than fulfilled expectations. The MFS Faido was planned to be in favorable rock according to the geographical prediction. While a few relevant but small fault zones were predicted, these were not posed as major obstacles. However, in April 2002, faulty gneisses of low strength were encountered and rock started to loosen and fall at the face. Unexpected squeezing ground and faulted rock caused major headaches from almost the first days of work. A major redesign was needed for the Faido MFS work eventually, separating the crossover tunnels from the emergency station itself and shifting them 600m southwards into better ground. The final TBM drives from Faido towards the Sedrun section were also slightly shortened, with the additional length added to the Sedrun contracts, to balance out the completion times and bring the overall breakthrough forwards. Four Herrenknecht machines, with

The required concrete was mixed directly on the spot and distributed with the help of the Betonzug.

a length of more than 400 meters and cutterheads measuring 9.5 meters, have excavated more than 85km of the main tubes approximately 75 % of the tunnel's main route. Gripper TBMs are specialists for hard rock. With two gripper plates, the TBMs brace themselves against the rock on both sides. The thrust cylinders push the TBM forward. The right and the left grippers can be controlled individually. This means that the TBM can master curves easily. The rotating cutterhead presses the disc cutters with high pressure against the rock. The disc cutters break the rock into saucer-sized chips. The excavated

Shotcrete primary lining on a crossover cavern.

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material is passed through openings in the cutterhead onto the belt conveyor and transported out of the tunnel. Directly behind the cutterhead, roof bolting units drill holes along several meters of length in order to put the roof bolts into place for rock support. Additionally steel rings, arches and mats are installed to stabilize the rock (if required by the geological conditions). A shotrete robot rotates around the TBM's longitudinal axis to provide final rock rock. The transport of the excavated rock out of the tunnel and materials into the tunnel is carried out via the rear part of the machine, the back-up system. Two Herrenknecht TBMs, Gabi I and Gabi II, of diameter 9.58 meters, were used were used for tunneling the Amsteg-Sedrun section. Tunneling commenced in Oct 2003 and Jan 2004 and was successfully completed in June & Oct 2006, 9/6 months earlier than planned. On June 16 and September 16, 2009, the two Herrenknecht Gripper TBMs, Gabi 1 and 2, completed the northern Erstfeld-Amsteg section with a length of just over 7 kilometers. Deviation from the ideal axis measured only 4mm in the horizontal and 8mm in the vertical. Regular tunneling started in Jan and Feb 2003 in the southern section of Bodio-Fadio using “Heidi” and “Sissi”, two Herrenknecht Gripper TBMs of

ROTHO - Robert Thomas Metall- and Elektrowerke GmbH & Co. KG

MRT Chemicals Pvt. Ltd

Bajaj Products


The fully complete excavation schematic of the 57km long rail tunnel

diameter 8.83 meters. After just 200 meters, the tunnellers were slowed down by the discovery of kakirites, since every meter of tunnel driven was to be secured in a complex process. In fall 2006, breakthrough was made in Faido when the TBMs reached their targets after 13.5 and 14 km respectively, with vertical and horizontal deviations of only a few centimeters.

In July and Oct 2007, both “Sissi” and “Heidi” entered the second construction phase towards Sedrun with cutterheads of 9.43 meters. On October 12, 2008, both the Herrenknecht TBMs successfully crossed the Piora Basin a funnel-shaped formation filled with sugargrained dolomite and water that reached deep into the rock of the mountain range. This had been the

most intensely explored section in the beginning of the project but after examining drill cores, temperatures and seismic results, geologists concluded that the bottom of the Piora Basin was sealed with gypsiferous cap-rock. A rock fall in the western tube and the subsequent stabilization measures interrupted tunnelling here until July 2010. The final breakthrough by “Sissi” and “Heidi” came in Oct 2010 and Mar 23, 2011, the latter amidst live media coverage from different parts of the world. The estimated final cost of the project was CHF9.4bn (US$9.0bn) for the Gotthard. These amounts exceed the original estimates, with the Swiss parliament approving reserves for uncertainties that included geological conditions, engineering issues and technological developments, the latter relevant due to the long project timescale. In the Gotthard Base Tunnel, lining work in the Erstfeld, Sedrun and Faido sections is progressing according to plan. At the end of December, the track crossover door for Sedrun North was transported into the tunnel and is currently being installed. AlpTransit Gotthard Ltd. will hand over the tunnel to Swiss Federal Railways (SBB) in operating condition at the end of May 2016. Until then, the focus of construction work will be on the tunnel lining, infrastructure systems and railway installations. This work has already started in the previously completed sections of tunnel in parallel with the final driving and concrete-shell construction activities. Picture Courtesy

A rear view of the driller head of the Tunnel Boring Machine that created the 57 kilometer-long Gotthard Base Tunnel in Switzerland.

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www.excavations2012.wordpress.com www.tunneltalk.com

INSTRUCT


Marol Maroshi Tunnel: Quenching Mumbai's Thirst Bhavani Bhavani Balakrishna Balakrishna

T

he Hindustan Construction Company (HCC) recently completed the construction of a12.4 km Marol Maroshi tunnel. Constructed under the Jawaharlal Nehru National Urban Renewal Mission (JNNURM), the project is part of the rehabilitation and improvement of the drinking water conveyance and distribution system from Bhanhup Treatment Works to Western Suburbs and Southwest part of the Mumbai city, which consists of Vaitarana, Upper Vaitarana, Bhandup, Maroshi, Tansa (East) and Tansa (West) main pipelines. Bhandup-Maroshi main pipeline runs up to Maroshi only and supplies water to the Veravali Group of Reservoirs. Other mains continue to carry water to Dharavi, Mahim and further. HCC bagged the project in September 2007 with a total contract

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value of ` 415.10 crore. The new tunnel will be replacing the existing Vaitarana, Tansa (East and West) main pipelines. The tunnel will have many advantages over existing surface pipeline. It is secured at a depth of 70 meters below ground level and cannot be tampered as it happens in case of surface pipelines. Hence there are fewer chances of leakages and pilferage of water. It will require minimum maintenance as the entire tunnel is made of concrete unlike surface pipeline which corrode over a period of time. The 12.4 km tunnel will be 3.60 meters in diameter and will have three new shafts at Maroshi, Vakola and Mahim besides the existing shaft at Ruparel College. The shafts are 12 meters in diameters and around 70 to 80 meters deep which is equivalent to 22 to 26 storied buildings. Two tunnel boring machines of 100


meters length weighing 150 tons were lowered in the shaft piece by piece and assembled at the bottom of each shaft before commencement of tunneling work On an average 20 meters of tunnel was completed in a single day with a record of 40 meters tunneling completed in a single day with a Wirth Tunnel Boring Machine (TBM). HCC has constructed 21 km of existing 26 km water tunnels that supply drinking water to Mumbai and is currently constructing 12 km of tunnels of the 23 km of water. The Bhandup Complex to Charkop tunnel of 12 km length was the last tunnel completed by HCC. This tunnel was completed 5 months ahead of schedule, despite difficult geological conditions. Come September 2013 and Mumbai will start getting flawless water supply from the new tunnel. After a number of impediments such


as difficulty in maintenance, security issues because of the pipes passing beneath the Mumbai airport land, the Municipal Corporation of Greater Mumbai (MCGM) decided to construct a tunnel from Marol Maroshi up to Ruparel College. By September 2013, more than half of Mumbai's homes will enjoy better and consistent water supply minus the frequent cuts. The tunnel will be operational only by September 2013 because engineers have to complete the cementing work and construct around five to six shafts linking it to other smaller water distribution networks. Mumbai has a long history of struggling to deliver reliable and safe drinking water to its residents. In 2005, the Municipal Corporation of Greater Mumbai initiated a plan to move from an intermittent water supply, averaging 2 to 4 hours per day, to a 24x7 water supply while managing to serve its rapidly growing population. The city

has already invested heavily in the expansion of water systems, yet the rate of population growth, compounded by instability of the water supply have hampered progress. It is said that over

20% of the daily supply of water is lost due to leakage or pilferage. The authorities decided to do away with pipelines and construct underground tunnels below Mumbai city to transport water.


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Stirling Lloyd Maintains Cut and Cover Tunnel Success in Hot Aggressive Climates its growing reputation R einforcing in the global tunnelling market, Stirling Lloyd's Integritank waterproofing membrane has recently been utilised to cope with the challenges of two major cut and cover tunnel projects in the Arabian Gulf. Built in response to significantly increased passenger capacity, the New Doha International Airport in Qatar has a transport infrastructure built around two major cut and cover tunnels. The Midfield Access Road Tunnel crosses under the airport's Western Runway and provides key access to the midfield development area and passenger terminals. The second tunnel accesses the Free Trade Zone which includes a business park, offices and several luxury five star hotels. With a successful track record of over fifteen years of waterproofing cut and cover tunnels, Stirling Lloyd's Integritank spray-applied membrane

NDIA - Long External View of Tunnel

was selected by main contractor and in-house designer, Benaim, for waterproofing the wall and roof slab surfaces of both these cast-in-situ cut and cover tunnels. Benaim chose this fully bonded, seamless system as it offered excellent resistance to the site's

Application of the first coat of Integritank

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high concentrations of groundwater chloride and sulphate and they had confidence in the product gained from working with the material previously in Hong Kong. Some 48,000m² of the Integritank two-coat system was spray-applied to the Midfield tunnel and 38,000m² on the Free Trade tunnel. A key consideration throughout for the client was the unique quality control system that is implemented during the twocoat, colour contrasting application of the membrane. These features were also important on a separate tunnel and road infrastructure project for the Department of Transport in Abu Dhabi. The Ras Al Akhdar and Baynounah Street improvement works includes two tunnel packages; Package 1 involving a 700m, two-lane tunnel to alleviate traffic congestion at the intersection between Baynounah Street and Sultan Bin Zayed Street, and Package 2, a 540m, two-lane, U-shaped tunnel which will provide direct access to the Etihad Towers. With Integritank again specified,

Sreerama Industries

Relyon Facility Services Pvt.Ltd


adhesion tests were initially carried out on each section of both cut and cover tunnels to confirm that the bond strengths achieved were in excess of those required, an important factor in ensuring a long service life for a coating. On completion of these adhesion tests, the concrete substrate was then primed with Stirling Lloyd's PA1 primer. Some 10,590m² of Integritank and 9,200m² of PVC T-lock liner was then applied to Package 1 tunnel and 14,000m² of Integritank and 16,000m² of PVC T-lock liner on Package 2. Each coat of the membrane is pigmented in contrasting colours, the first yellow, the second grey, so the sprayer can visually check that the correct thickness of material has been applied. This is also backed up by constant wet film dipping to ensure the required 1mm for each coat has been achieved. This latest UAE project was awarded as a direct result of Integritank's successful application at the Yas Island Southern Tunnel Crossing, completed in Abu Dhabi last year. Named a couple of years ago as the 'world's leading tourism project' at the World Travel Awards, Yas Island's development has relied heavily on investment in its construction and transport infrastructure and one central

View of Yellow Integritank on Wall

feature has been the Southern Tunnel Crossing, which opened in October 2010, connecting Al Raha Beach to many of Yas Island's key attractions. Although an immersed tunnel, this was actually built by cut and cover methods between two coffer dams that held the water back during construction. On this 1.2km long, 40m wide and 10m high tunnel, Integritank was again the

principal waterproofing system, applied to some 49,000m² of concrete wall and roof slab. As was the case on the subsequent Ras Al Akhdar tunnels, one potential issue for the project's success was the Abu Dhabi climate. The hot and humid weather can cause problems for the installation of other liquid applied systems, however, Integritank's advanced methyl methacrylate (MMA) resins are probably the most tolerant of climatic conditions and this enabled it to be successfully applied in temperatures in excess of 40°C. Once the Southern Tunnel Crossing had been completed, the coffer dams were removed and, though the tunnel is now immersed under 25m of sea water, the seamless, high performance waterproofing membrane has ensured it has remained 100% dry after over 18 months of service.

For further details contact: Andrew Crosbie, PR Director Ph: +91-7947-992022

Dave Mulligan Stirling Lloyd Marketing Manager Ph: +91-1565-633111 E-mail: [email protected] Web: www.stirlinglloyd.com

View of Works inc High Rise in Background

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Crush and Convey: The Only Answer to Tackle Present Day Surface Mine Economics

Abhishek Jain

Vaibhav Singhal

Final Year M.Tech Student, Dept. of Mining Engg, IIT,Kharagpur

Final Year M.Tech Student, Dept. of Mining Engg, IIT, Kharagpur

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his paper is an attempt to look into different mine equipment parameters and selection of equipment for environmental friendly and cost effective solution for open cast mining with special reference to coal and limestone. While cost of every resource is on an increasing trend including fuel prices, on the other hand the demand for reduced carbon emission is mounting day by day. A mine investor or operator has no other alternative but to design, plan & operate a surface mine according to his needs of the day. Crushing and conveying the mineral and waste/rejects as against handling ROM directly from the face, transporting it by diesel bund transport system. Crushing and processing at the pit top and then further long haul to the final destination of the mine product including handling and transportation of multiple volumes of waste is always not only economic but takes care of the environment and is better organized. Economics of a mining operation is a subject of efficiency of each and every operation along with consistency of the set mining standards and methods and finally the performance of equipment's and their overall quality. It is however not to be out of subject to remind that long term planning of mining operation and equipment including proper selection of equipment and resources play a vital role to operate a system economically and ROI of the project. The discussion of the subject here shall be restricted to open cast limestone and coal mining to understand the above as mentioned. Present Trend of Surface Mining of Limestone and Coal in the Country While attempt was made to mechanize the underground coal mining in the country especially by longwall mining, continuous miner and blast gallery method; the results are not very encouraging. The open cast mining in coal and limestone, for that matter, even other minerals like copper, zinc and iron ore have traditionally been handled by shovel dumper method. However continuous mining by bucket wheel excavator has been a success in coal mining belt in southern sector of the country. Implementation of the dragline mining although has been made successful in Indian coal mines though achievements are not so encouraging so far. Surface miners have been a recent trend in both limestone and coal mining in the country. Although the government run

companies are yet to take direct responsibilities, contract mining has been very successful. On the other hand, the cement plant owners in selected projects have implemented a complete environmental friendly blast free mining by surface miners on a large scale. Because of the limitations of cuttability of surface miners within the economic range, the implementations in limestone mining could not be extended further. Once surface mined by surface miner the ROM are sized and beltable. However transportation of the material or surface mined ROM is done by trucks or heavy dumpers. Attempts are yet to be madein the country to convey the sized ROM by belts directly from the pit to the final dispatch point either in limestone or coal. There have been continuous improvement in the sizes of loading or transport in the sizes of loading or transport vehicles in the mines thereby encouraging the cost per ton. Consideration of In-Pit Crushing Implementation of in-pit mining technology for coal and other minerals need due consideration of geo-mining condition of deposit. Availability of in-pit crusher and shiftability of in-pit crusher in the mine are other consideration which needs to look into. Shortening travelling distance and cycle time between excavation and crushing operation require fewer trucks and leads to less dust generation and also decreases on site traffic conjunction which is a factor to be considered in favour of belt conveyor system especially in large open cast mines. This leads to safer mine conditions and also contributes in relief against fatigue mine management of large dumper logistic truck maintenance and haul road maintenance. Most of the opencast mine in country are governed by high stripping ratio, thereby planning and operation of opencast

Rockster R1100 crusher in Baranj O.C.P


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mine primarily determined by removal, transportation and dumping of overburden. While in-pit crushing is profitable proposition, installation of crusher and conveyor can be inflexible and unwieldy. Pit geometry, depth, operating stripping ratio and mine access are the parameter which needs to be study for implementation of in-pit crushing and conveying.

directly transfer out of the pit. Depending on the pit geometry and depth, there may be more than one transfer belt junctions. Once the material is out of the pit it is conveyed to the plant of final destination.

Evaluation and Implementation on In-Pit Crushing Design capacity of crusher and conveyor system are required to be co-ordinated between material handling engineer and mine planner. As very first step hourly tonnage and expected belt profile must be determined, secondly it must be established to determine how big and how long should be the conveyor system. Finally establishing the required operational range of material handling system and consider the function of mine throughout and not only just the peak should be considered. Estimation of number of loading equipment which will deliver to the crusher followed by calculation of maximum hourly production in terms of number of shovel and the trucks needs to be estimated.

Belt conveyor system for transport from the pit itself

Mine planning is very critical in implementation of in-pit crushing and conveyor. Installation of crusher and conveyor must be planned well in advance simultaneously with haul road. Excavation or placement of material to establish conveyor route and crusher station should be planned as mining started. Access geometry for haul road, crusher, belt way etc. is also established as mining proceed. Detail time sequence planning and evaluation of precise working geometry are must as installation of crusher and conveyor can be inflexible and unwieldy. A combination of conveyor transportation and truck haulage-dual system can be most cost effective. While conveyor system for transportation of material is most cost effective, truck haulage system can be justified for mine with different kind of materials. A particular material may be of insufficient quantity or scattered in several areas of the pit. In-Pit Crushing Conveying Scheme The ROM material is dumped into a feeder pocket within the selected pit after crushing by in-pit crusher. The face material is transported by dumper, lying within pit, from the face to feeder hopper installed on ground level. From the ground hopper fed onto the horizontal on the pit or it can be

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Typical Conveyor Layout with BWE. (Can be also with In-Pit Crusher System)

Conclusion Truck and conveyor combination system can avail the advantage of both the system while flexibility is assured through dumper transportation within the pit, operating cost per tonne for material conveyed out of the pit especially on uphill long slope is cheaper. Reduced number of dumper not only lowers the capital investment but at the same time lower the running cost. “Carbon emission” which is not only a threat to environment but also consideration of future financial threat “is not far from where there can be implementation of carbon tax”. Dust pollution is another major hazard to mine environment and surrounding is greatly reduced by crush and convey system. However implementation of limited number of truck within the pit may also lead to the solution to dust generation within the pit and maintenance of haul road. This can be achieved by stabilizing the upper layer of haul road including strengthening of base by addition of aggregate and additives in in-situ material. At the end it can be concluded wherever applicable and possible truck and conveyor system should be attempted.

Belt conveyor system with top cover to the final dispatch point

For further details: Rockster Recycler India pvt. Ltd.

No. 500, 17th Cross, Ideal Home Society, RR Nagar, Bangalore - 560098, Ph: +91-80-28604528, E-mail: [email protected], Web: www. Rocksterindia.com

Roof India


In Conversation with Mr.Ajay Maini, Director, Maini Construction Equipment

Ajay Maini, Director, Maini Construction Equipments Pvt Ltd

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ith a proven track record of manufacturing and supplying quality products, Maini Construction Equipments Pvt Ltd, has established itself as a leading name in the formwork industry in India. An ISO 9001:2000 certified company, with a strong customer focus; Maini is considered a trendsetter in the field of modern aluminium formwork systems in the country. Under the dynamic leadership of Mr.Ajay Maini, Director of the company, Maini has grown from strength to strength and is now a preferred choice of contractors and engineers. The company began its eventful journey in 1986 when Maini Scaffolding Company was started. Earlier the company was a dealer. By 1996 it had entered the mainstream and had made deep inroads into the market

with direct marketing initiatives. The company started manufacturing aluminium formwork in 2008 and has now carved a niche for itself through its R & D focus, innovative product range, and excellent technical support services. Speaking exclusively to the Masterbuilder, Mr.Ajay Maini gave insights into the company's product range, the general state of affairs of the formwork industry in India and their future plans. Here are excerpts from the interview. Give us an overview of your range of scaffolding and formwork systems? Maini Construction Equipments Pvt. Ltd. (MCE) are one of the leading manufacturers of complete range of aluminum formwork systems right from designing, manufacturing, erection to the complete site support and regard to scaffolding, we offer complete range of steel scaffolding including cuplok systems, props, spans, metriform, wall form and tailor made formworks etc. Apart from the technical attributes of your formwork systems, what are the other value added services that you offer as part of your total product package? MCE not only provides the best quality products but also provide solutions and key inputs for special

structure formworks and assist our customers technically to reach the desired results. Give us a few examples of infrastructure projects where your products have been used? In steel scaffolding, we have successfully executed residential and infrastructure projects including Bridges at Karnal to Ambala, Highway for National Highway Authority of India, Allahabad-Naini Bridge, Mumbai-Pune Expressway, Delhi Metro, Kolkata Airport, Delhi Airport etc. In aluminum formwork, a few of our projects includes Salapuria Greenage project Bangalore, Ozone Metrozone Chennai, Marg Ltd. UPHDB, Lucknow Development Authority etc. Has the recent economic slowdown impacted your order book? Not really, because of our versatile range of products in steel as well as aluminum formwork. MCE's aluminum formwork was launched when the entire industry was going through a rough phase, however, we were able to sustain and managed a steady growth. Given the various advantages of system formwork, why do you think has been the growth rate not up to expectations in the Indian market? Is it because of reluctance on the part of the engineering community or lack of codes or is it the cost factor? Yes, given the various advantage of system formwork the growth rate is not up to the expectations because of the lack of skilled and educated labour at the level of installation. Another reason is the fact that many are taking a short cut to cut cost rather than adhering to the complete system, thus, resulting into not getting the desired results.

For further details: E-mail: [email protected] Web: www.mainiscaffolding.com

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'Next - Gen' Fiberglass Shuttering Systems from Indigo

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apid advancements in technology in the field of formwork have seen the advent of several new innovative products in the market in recent times. While there are several product offerings which could lay claim to being innovative, there are only a select few which carve a niche for themselves. Epic Eco fiberglass formwork systems are among these top notch products. Epic Eco fiberglass formwork systems come from Epic Group, a globally renowned formwork specialist, whose products are being used in across continents. The Epic Group is represented in India by Mumbai-based Indigo Multitrade Pvt Ltd. Epic Eco Composite Fiberglass shuttering building systems represent a revolution in the area of shuttering because of their lightness, simplicity, durability, solidity, resistance to temperature changes and their price competitiveness. One of the major advantages with these systems is that they offer simplification of shuttering with the same mechanical properties of other systems. Epic Eco fiberglass formwork systems display excellent mechanical qualities since they can hold 60kN/m2,-1200 psf

of paneling. They are made up of a composite mixture of polypropylene, special fibers and chemicals which enables the construction to hold such high pressure. Moreover, the speed of paneling with these systems is very fast and abundant palette of elements allows for best possible paneling composition. Optimum paneling composition is ensured since the paneling surface is very close or in some instances the same as the surface wetted with concrete. Epic Eco paneling systems are particularly suitable for paneling of foundations, shafts of all kinds, and walls up to 4.2 meters / 14 ft height. They are also suitable for handwork because of their low weight, i.e., 18-22 kg/m2, together with the connective material. The paneling system consists of 10 elements and 51 connective elements, which are suitable for all heights. The lightweight of the Fiberglass paneling system also means that they are easy to transport. Adding to their sustainability quotient is the fact that the paneling systems are recyclable. In fact, they are brought back by Epic Group for the market price.

Excellent finish is ensured because of perfect treatment of elements and optimal joints. Cleaning of the panels is also easy since concrete does not hold the surface. Another highlight of Epic Eco paneling systems is their ability to withstand extreme vagaries of temperature, making them ideally suited for varied climatic conditions. They can withstand temperatures of even -23 degrees Celsius / - 9.4 Fahrenheit or up to +50 degrees Celsius / + 122 degrees Fahrenheit without experiencing any damage. Since the systems do not decompose or oxidize, the panel systems are durable and last for at least 10 years and is maintenance free. The innovative production process means that the company is able to pass on the cost advantage to the end –user, ensuring the cost competitiveness of Epic Eco Composite Fiberglass shuttering systems. Adding to the cost advantage is the fact that they are light in weight and are therefore easier to transport. Given the slew of advantages offered by this innovative shuttering system, plus the excellent technical support services provided by Indigo Multitrade Pvt Ltd, it is not surprising that Epic Eco Composite fiberglass formwork systems are now gradually becoming the preferred choice of contractors and engineers around India.

For further details: Indigo Multitrade Pvt. Ltd.

416, Bhaveshwar Complex, Vidyavihar(W), Mumbai - 400086, India Ph: +91-22-25021144, 40111466, Fax: +91-22-25025994,

E-mail: [email protected] Web: www.indigo.in


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Making a Mark with Modular Tunnel Formwork Systems

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aruti Steel Fab (MSF) is one of the leading formwork and scaffolding company in the country. The company has been a frontrunner when it comes to introduction of innovative products and solutions. Over the past 12 years, from its inception, it has become a name synonymous with a quality range of heavy duty formwork and scaffolding systems in the country. The company offers a comprehensive range of modular tunnel formwork which enables efficient and cost-effective in –situ casting permitting walls and slabs

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to be formed simultaneously in one operation with a high degree of accuracy and excellent finish. The company has carved a niche for itself in modular tunnel formwork systems, an area which requires a high degree of specialization. The specialty of MSF tunnel formwork includes it being collapsible tunnel form, resusable tunnel form, lightweight tunnel form and importantly, allows helps in speeding up the construction process. The systematic approach of the company means that the team of


highly experienced professionals, who are at the helm of affairs, thoroughly analyze every detail of the project based on the structural plan, in close tandem with the clients, and offer the right solution.

For further details: Maruti Steel Fab

109, 1st Floor, Gera Garden Bldg. 1, Koregaon Park Road, Pune-411001 Ph: +91-20-26056282, Fax: +91-20-26056282 E-mail: [email protected], [email protected] Web: www.marutisteelfab.com


Waterproofing Solutions for New and Old Structures

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aterproofing is the process of applying a special membrane or sealant to a surface in order to stop water from penetrating the structural areas of a building. Roof, floor, wall, basement, kitchen, shower and toilets are the areas those can be effectively saved from leakage, seepage and dampness by using different waterproofing solutions. It is also used in pools, planters, lagoons, tunnels and dams to prevent water leakage. Traditional waterproofing systems like brickbat coba, mud faska etc require a lot of time for execution and also add to the dead load of the roof leading to short life expectancy. Now a days, the time is a major factor and hence new waterproofing materials have been adopted for the following reasons: To reduce time & labour, to increase the life expectancy of the structure and to be compatible with weather conditions. Modern waterproofing systems include Polymer modified Bitumen Membranes with different kind of reinforcements, Single Ply Membranes and Liquid Applied Membranes. The technical properties of these waterproofing membranes are mainly measured in terms of Softening point, Penetration, Cold flexibility, Tensile strength and Elongation etc. These membranes can be fixed by different methods such as fully bonded, partially bonded, mechanically fixed, loose laid and ballasted or any of the combination as per the

APP Bituminous Membrane

Liquid Waterproofing – PU Based

requirement of the site. One should consider the type of surface, application, slope, insulation, vapour barrier and end user requirements while choosing waterproofing material.Texsa is manufacturing & marketing Polymer modified Bitumen based waterproofing membranes under the brand name of MOPLY & TEXSELF (Atactic Polypropylene & Styrene Butadiene Styrene modified reinforced with Polyester felt or fibre glass).These membranes are manufactured from high grade bitumen blended with polymers to obtain low cold flexibility (-5o C to -20o C) which is indirectly related to the durability of membrane whereas the type of reinforcement used determines the tensile strength, tear strength, puncture resistance and other mechanical properties. Other benefits of using these membranes are uniform thickness, effective in thermal and structural stresses, self finished, user friendly, fast execution of job etc. Bitumen membranes have life expectancy of 10-15 years or more. Another type of membrane waterproofing is by Single Ply Membranes. These are flexible sheet material, elastomeric or thermoplastic in nature used in one ply configuration as roof waterproofing membranes. PVC (Polyvinyl Chloride) single ply membrane, marketed under the brand name of VINITEX and TPO (Thermoplastic polyolefin) membrane under the trade name Texsalon are in

Texsa's waterproofing product range in India. PVC roof membrane has the longest track record of any thermoplastic membrane with the first PVC based systems initiated in Europe in early 1960. It has high resistance to puncture, impact, fire and microbiological attack. It is flexible to low temperature and tolerant to high temperature and life expectancy of PVC membranes is 25-50 years. Te x s a o f f e r s s p e c i a l P V C membranes for waterproofing applications in swimming pools, tunnels, potable water tanks besides the standard grades. Liquid Applied Membranes, are amongst the popular materials used for waterproofing where faster installation without joints is required. These Liquid membranes are light weight having very high elongation and elastic recovery. It is mostly used on complex roofs and damp surfaces. As there is no need of torch on application, it is user and environment friendly. With high UV resistance and durability, it is available in different colours. Texsa offers cold Liquid applied waterproofing in the form of – Acrylic, PU coatings and bitumen coatings. Thus, Texsa offers all types of products for providing a waterproofing solution. Texsa India Ltd. is a wholly own subsidiary of the TEXSA Group founded in 1954 in Barcelona (Spain). Texsa manufactures and markets products for roofing/ waterproofing, thermal and acoustic insulation and geotextiles, as well as the corresponding auxiliary materials for each of these fields, for building and civil works.

For further details: Texsa India Ltd.

345, Ground Floor, Udyog Vihar Phase II, Gurgaon – 122016 Haryana Ph: +91-124-4052078/79, Fax: +91-124-4052080, E-mail: [email protected] Web: www.texsa.com


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Construction Chemicals International Conference

Catapults CCMA into National Limelight MB Bureau Report

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he Indian construction industry had set a scorching pace of growth by the turn of this century. The growth story, although impacted by the vagaries of the global economic uncertainties in recent times, has been fuelled by the inherent demand for infrastructure development and the boom in the real estate sector over the past two decades. The construction industry continues to be the second largest employer after the agriculture sector and with the government recently announcing plans for investing ` 50 lakh crore in infrastructure development during the 12th Five Year Plan period; it is a growth story that is expected to continue in the near future. One of the direct beneficiaries of this growth story has been the construction chemicals industry, popularly referred to as the 'Sunrise Industry'. While there is no denying the fact that the construction chemicals industry in the country has been growing at a healthy

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rate, industry analysts had always felt that the growth rate was not keeping up to the actual potential. Several factors including, a general lack of awareness about right usage of construction chemicals among a vast majority of contractors and a dearth of trained applicators had been attributed to the relatively slow growth of the construction chemicals industry. This was the overall scenario of the construction chemicals industry, until CCMA happened. The formation of the Construction Chemicals Manufacturers Association (CCMA), a few years ago, came as the much needed trigger for boosting the fortunes of the construction chemicals industry. The industry association has now become the voice of the construction chemicals manufacturers and has come out with several key initiatives that have put the construction chemicals industry on an accelerated growth path.


C3 At the Right Time According to industry experts, over 85% of contractors in the country are said to be not fully aware of the uses of construction chemicals. Setting right this general lack of awareness about proper usage of construction chemicals is one of the main objectives of CCMA. The association has been conducting several seminars and training programs for applicators, thereby bringing into sharp focus the key role that the construction chemicals industry can play in the nation building process. As part of its initiatives, CCMA had recently successfully hosted India's largest International Conference on Construction Chemicals (C3) on 17th and 18th of February, 2012, at Hotel Ramada, Powai, Mumbai. The central theme of the conference was,

'Emerging Material, Methods & Practices', in the field of construction chemicals. Speakers at the conference included, the virtual 'whos who' from the world of construction chemicals, drawn from academicians, scientists, and industry professionals, from around the world. The conduct of C3 could not have been timed better. The country is entering its crucial second phase of infrastructure development and the eyes of almost every other industry is towards the construction industry, as it is the one that plays a key role in the process. The larger scale of projects, which has pushed up demand for high-strength and quick setting concrete, plus the greater emphasis on quality, has automatically made a positive impact on the construction chemicals market. The Sun Rises It won't be a misnomer to say that with C3 the sun has really risen, as far as the sunrise industry is concerned. A fledging industry has now taken its rightful place in the pantheon of top industries in the country .The pace of development of technology, as well as usage of


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Samir Surlaker President, CCMA

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“C3 has set the ball rolling for the conduct of a series of roving seminars around the country, to further the cause of proper usage of construction chemicals”


Presentations

} Construction Chemicals A Building Developer's View by Mr.C.K.Pithawallah, Hiranandani Group } Self-Compacting Concrete for Mass Housing by Mr.Charles Jones, BASF India } High quality Sealants and Life Cycle Management by Mr.Ashraf Wahib, Sika IMEA region

Presentations

Session Chairman: Mr.A.R.Jambekar, S.N.Bhobe & Associates } Use of Microsilica in High Performance Concrete by Mr.Per Fidjestol, Elkem AS, Norway } Roof Waterproofing & Insulation by Mr.Sanjay Bahadur & Mr.Padmakar, Pidilite India } Right Technologies for Trouble-Free Tile and Stone Installations in Bathrooms and Kitchens by Dr.P.Arjunan, MYK Laticrete

Technical Session III: Solutions for Institutional Buildings Presentations

construction chemicals has received the necessary fillip with the successful conduct of the mega conference, which saw dignitaries from around the world, share their wisdom with industry professionals, academicians, scientists and students from around the country. The importance of the conference, vis-à-vis the growth of construction chemicals industry cannot be overemphasized. As rightly pointed out by Mr.Samir Surlaker, Chairman, CCMA, C3 is a huge step forward in increasing awareness about construction chemicals in the country. Just as the Indian infrastructure development story enters its second phase, C3 has signaled the entry of the construction chemicals industry into its crucial growth phase. The key focus areas of CCMA were a subject of intense discussion during the conference within the delegates and among the various participants. “Standardization and training would be among our two top key focus areas,” observed Mr.Samir Surlaker, further stating that C3 has set the ball rolling for the conduct of a series of roving seminars around the country, to further the cause of proper usage of construction chemicals. The growth story of CCMA also makes for fascinating reading. It is really interesting since it is perhaps the only industry association whose members are engaged in intense competition in the marketplace, a point that was bought out Mr.R.K.Jha, Director, Gujarat International Finance Tec-City (GIFT), during his inaugural address at the conference. The association has grown to include over 35 member-manufacturers within a remarkably short span of time. C3 saw every top player in the field of construction chemicals rub shoulders

Session Chairman: Mr.Barry Jackson, Consultant, Dubai

Technical Session II: Session Chairman: Prof.M.S.Shetty

Session Chairman: Mr.A.T.Samuel, STUP Consultants } Construction Chemicals An User's Perspective by Mr.C.R.Dordi, Ambuja Cement } Structural Versus Non-Structural Repairs- A Consultant's Views by Mr.Satish C.Dhupelia } Reliable Waterproofing Solutions from Basement to Roof by Mr.Arijit Basu, Sika India

Technical Session IV: Solutions for Transport & Water Infrastructure Session Chairman: Dr.N.V.Nayak, Gammon India Presentations

Director, Gujarat International Finance Tec-City (GIFT)

Technical Session I: Solutions for Mass Housing Buildings

} Future of Tunneling Technologies by Mr.Willey Kay, WAK Technologies, Singapore } Construction Chemicals- A Contractors View by Mr.Manish Mokal, Gammon India } Case Study: Advanced Concrete Technology for Tunnel Segments by Mr.Eugen Kleen, MC Bauchemie, Germany

Technical Session V: Solutions for Industrial & Power Projects Session Chairman: Mr.C.R.Raikar, Structwel Designers & Consultants Presentations

R.K.Jha

“It is indeed laudable that construction chemicals manufacturers, inspite of being competitors, have come together to share a platform for the greater cause of growth of the construction chemicals industry”

} } } }

E-Chem Repairs, A Modern Approach by Mr.M.N.Ramesh, Savcor India Grouts for Machine Foundations by Mr.Rakesh Shah, Fairmate Chemicals Precision Grouts by Mr.Prabhakar Sharma, Pidilite India Customized Flooring Solutions for Industrial Establishments by Mr.N.Gopinath, Sika India

with each other, all for the greater cause of the promotion of the industry, something that is remarkable in this day and age of intense competition. Unprecedented Success The conference perhaps marked the first time that such a conglomeration of leading players in the field of construction chemicals shared a common platform towards achieving a common goal, in the country. It also offered delegates a chance to get detailed insights into various aspects of construction chemicals from renowned experts, keeping in tune with one of the key objectives of CCMA, i.e., dissemination of knowledge in the field.


The formation of CCMA has meant that construction chemicals manufacturers can now be assured of the fact that their requirements would be put across to various different authorities for the further growth of the industry, a factor that was earlier considered one of the growth inhibitors. In fact, as part of the conference, it was resolved that the views of the members would be put forth before the central and state governments. CCMA is already working in close tandem with other leading industry bodies with respect to liasoning with various government authorities for the betterment of the construction chemicals industry. The conference also helped in highlighting the ambitious training initiatives that CCMA has lined up for conduct around the nation. CCMA has also announced its plan to come out with a detailed handbook on the proper usage of construction chemicals, which it would be publishing with help from ICI. The association has also been meeting technical institutions for including certain topics pertaining to construction chemicals as part of the academic syllabus. The widespread attention that C3 garnered, among academicians, industry professionals, students, and civil engineering fraternity, augers well for CCMA further intensifying its efforts towards conduct of specialized training programs for various stakeholders from the construction industry.

Challenges Ahead The success of the conference has also meant that the real test for CCMA begins now. All the eyes are now on the association, which is expected to help the construction chemicals industry surmount challenges that lie ahead, such as lack of standardization, codes , rationalization of tax structures, etc. The onus is now on CCMA to address key issues that have been hindering the growth of the construction chemicals industry in the country. CCMA has already started the process and has now firmly entrenched itself as the voice of the construction chemicals manufacturers. One of the biggest breakthroughs for CCMA has been that BIS has co-opted the association in IS codal committees and will play a key role in hastening the process of IS codes for new technologies. A rapidly evolving customer and his changing demands is another area that the CCMA has to take care off. Lack of standardization and entry barriers is another one of the tough challenges facing the construction chemicals industry today. These factors have meant that the construction chemicals market continues to be dominated by the unorganized sector in the country, leading to skewed competition. It is in this scenario that the coming together of leading players under the banner of CCMA bodes well for the growth of the industry. As mentioned earlier, the success of C3 could well prove to be the trigger that helps CCMA surmount the challenges and put the construction chemicals industry on the fast track. With the sustained emphasis on infrastructure development and the push being given to affordable housing, the construction chemicals industry in the country could be in for its most exciting growth phase in the near future.


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Events Stimulus 2012

UltraTech 'Stimulus 2012' MB Bureau Report

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n Feb 22nd, 2012, some of India's brightest, budding civil engineering students had their mettle tested on questions related to concrete and construction in “Stimulus”, Ultra Tech's Cement's civil engineering quiz program in South India. Ultra Tech's “Stimulus” has been the largest quizzing platform for civil engineering students and it lived up to its promise of being larger-than-life this year with participation from over 21,000 civil engineering students involving 400 engineering colleges across the states of Karnataka, Tamil Nadu, Kerala and Andhra Pradesh. “Stimulus” has reigned supreme as the ultimate battle of brains for civil engineering students and is the most coveted quizzing title for engineering colleges across South India in the civil engineering stream. Amidst an enthusiastic and cheering audience comprising civil

engineers performing different roles in the community, two teams each from the state of Karnataka, Tamil Nadu, Kerala and Andhra Pradesh battled it out at the Nimhans Convention Center in Bangalore for South India's top slots. Hosted by renowned quiz master, Mr. Giri Balasubramanian, the teams were subjected to creative but rigourous rounds like “Decode Stimulus”, “Lateral stimulus” and “ Visual stimulus” involving questions revolving around civil engineering fundamentals, practical applications and best practices. The team's colour-coded shirts and the buzz, excitement and nail-biting finish that kept the audience on the edge until the quiz master bowled what he dubbed as the final ball, was much akin to a thrilling twentytwenty cricket match. Even the veteran civil engineers and academicians in the audience caught the adrenaline rush

Winner and Runner of STIMULUS 2012 in South India final with UltraTech team

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as they vied with each other to tackle the googlies and bouncers thrown by the Quiz Master in audience questions section. Amrita School of Engineering, Coimbatore bagged the top honors of winning the south India final with a cash prize of ` 30000 while Alagappa College of Technology, Karaikkudi came second and won a cash prize of ` 15000. Nearly 800 national delegates participated in the program as live audience. The grand finale was preceded by state and regional rounds held in their respective states earlier. Organized by Ultra Tech Cement Limted, “Stimulus” is a civil engineering quiz program in South India to encourage and nurture the talent among the Civil Engineering Students. The students were selected from their respective colleges based on preliminary written tests. The regional rounds were


Salem

Cochin

Chennai

Winner of various regional rounds in Tamilnadu & Kerala Coimbatore

Madurai

Thanjavur

Vellore

Kozhikode

represented by 8 colleges and winners of the regional round participated in the state final and finally, the best two Courtesy: www.tu-freiberg.de teams from the state of Tamil Nadu, Kerala, Andhra Pradesh and Karnataka competed for the top slots. The regional round of Chennai was held at the grand Vivekananda Auditorium, College of Engineering Guindy on Sept 28, 2011. The preliminary round winners from IIT Madras (IITM), College of Engineering Guindy (CEG)-Anna University, SRM University, Bharath University, Hindustan University, B. S. Abdur Rahman University (new entrant), Dr. M. G. R. University and Velammal Engineering College (new entrant) participated. CEG emerged the winners after winning the nerve wrecking tiebreaker and walked away with a cash prize of `10000/-. They also qualified for the Mega Final while the runner up SRM University contended with the prize money of ` 6000/- and vowed to

come back with revived energy next year. The regional round of Vellore region held on the following day received enthusiastic response with colleges spread far and wide - in a range of about 200kms - eagerly participated in the contest. The participating teams, VIT University (VITU)-Vellore, Thanthai Periyar Government Institute of Technology (TPGIT)-Vellore, Arunai Engineering College (AEC)Tiruvannamalai (new entrant), Sri Venkateshwara College of Engineering (SVCE)-Sriperumpudur, Adhiparasakthi Engineering College (APEC)Melmaruvathur, Jayam College of Engineering & Technology (JCET)Dharmapuri and Sapthagiri Engineering College (SEC)-Dharmapuri left no stone unturned when it came to winning. SVCE emerged the winners while TPGIT came behind them. Salem Regional round was held on

Feb 6, 2012 at Sona College of Technology, Salem. The teams that participated included Government College of Engineering -Salem, Mahendra Engineering-Sale, S.R.College of Engineering and Sona College of Technology.Kongu Engineering College, Perundurai, Institute of Road and Transport Technology, Bhavani, MPNMJ Engineering College, Chennimalai, Erode Sengunthar Engineering College, Thudupathi. The regional round in Coimbatore held during Feb 9, 2012 attracted 1200 participants from colleges like PSG Tech - Coimbatore, Coimbatore Institute of Technology (CIT)-Coimbatore, Government College of Technology (GCT)- Coimbatore, Amrita School of Engineering (ASE)-Coimbatore, Sri Ramakrishna Institute of Technology (SRIT)-Coimbatore, Shri Krishna College of Technology (SKCT)Coimbatore, Karunya University (KU)-


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Coimbatore, PSNA College of Engineering and Technology-Dindugul. ASE-Coimbatore emerged the winners while PSNA came behind them. Another regional round was held on Feb 7, 2012 at Thiagarajar College of Engineering-Madurai.The teams that participated included Thiagarajar College of Engineering Madurai Kalasalingam University-Krishnankovil, Mepco Schlenk Engineering College -Sivakasi, Alagappa College of Engineering and Technology -Karaikudi, Raja College of Engineering & Technology-Madurai, K. L. N. College of Information Technology-Madurai, Vickram College of EngineeringEnathi, Mohamed Sathak Engineering College-Kilakkarai. Madurai went on with a record for the highest score (75 points as a winning team) in the South Indian STIMULUS. AC Tech. Karaikudi emerged the winners while TCE, Madurai came behind them. Thanjavur Regional round was held on 10th Feb'12 at Periyar Maniammai University Thanjavur. The participating teams are Periyar Maniammai University Thanjavur, P R Engineering College Thanjavur, Sudharsan Engineering college -Sathiyamangalam, Oxford Engineering College - Tiruchirappalli, Anna University of Technology-Tiruchirappalli, National Institute of Technology-Tiruchirappalli, M . I . E . T. E n g i n e e r i n g C o l l e g e Tiruchirappalli, Annamalai University-

Amrita School of Engg. Received the Winner Award

Chidambaram. The PREC, Thanjavur emerged the winners while NIT, Trichy came the runner. Cochin region saw participation from Sree Narayana Guru College of Engineering-Cochin, SCMS School of Engineering & Technology-Cochin, CUSAT-Cochin, Mar Athanasius College of Engineering-Kothamangalam, RAJIV GANDHI Institute of Technology-Pampady, SAINT GITS College of Engineering Pathamuttom, TKM College Of EngineeringKollam. Mar Athanasius College of Engineering Kothamangalam emerged the Winners. In the Kozhikode Region, NSS

AC Tech, Karaikudi received the Runner Award

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College of Engineering Palakkad emerged winners. Other colleges that participated include IES College of Engineering Chittilapally, Thrissur, Govt. Engineering College Thrissur, MES College of Engineering Kuttipuram, A. W .H Engineering College-Calicut, Govt. Engineering College-Calicut, N. I. T. Calicut and Govt. College of Engineering - Kannur. The winners and the runners of 6 regions participated in the Tamil Nadu Final with the Alagappa College of Technology, Karaikkudi and Amrita School of Engineering, Coimbatore winning in the event. The winner of the Cochin Region and Kozhikode region represented Kerala state in South India Final. The competition coincided with the 3 day conference on REDECON 2012 organized by Association of Consulting Civil Engineers (I) in which UltraTech Cement Limited was the principal patron. With an obvious gap between curriculum and the real world of construction, innovative and creative platforms like the “Stimulus” can help future civil engineers to acquaint themselves with the actual applications of theory and concept in the practical world. The Indian construction industry needs more such events wherein civil engineering students can interact with the people in the field.

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Revolutionary Solutions for Concrete Repair

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asy to use, factory packed, self curing, achieves high compressive strength - >3 N /mm2 in 4 hrs. and can be painted over, 24 hrs. after application – this is MortaRep SuperStrong a polymer modified multi purpose mortar for concrete and brick surfaces which can be easily applied on horizontal, vertical, and over head surfaces in a single layer and up to a thickness of 50 mm. Scenarios such as water seepage in mineral substrates, leads to carbonation and deterioration of the structure over a period of time, this is a natural enemy to the durability of any structure. Captain Bond offers products, which protect the structure against such seepages. MortaRep SuperStrong is a new introduction from Chowgule Construction Technologies Pvt Ltd. It combines - a) Anti corrosive coat b) Key coat for steel and concrete c) Waterproof and non shrink mortar and d) Concrete or plaster finish – all in a single product. Traditionally, repair of concrete

substrates is done using the Polymer Modified Mortar method. This process involves removal of the old / weak concrete areas, treating the exposed steel – removal of rust and application of anti corrosive coating, and building up of the removed concrete with site prepared sand / cement / polymer mortar in layers of 20 mm each, interspaced with curing. This process could take up to 7 days before the area can be handed over for further use.With MortaRep SuperStrong, once the damaged concrete is removed and the exposed steel in cleaned, the pre mixed and factory packed product is mixed with water – 5 ltrs. to 25 kgs of powder product, and then applied directly onto the substrate to be repaired. Once installed it is allowed to self cure for 24 hours and then can be over painted to provide a finished surface. A coat of CrystalFlex 2K SuperStrong powder is recommended over weak substrates before the application of MortaRep SuperStrong. Its unique properties include

MortaRep SuperStrong

high early compressive strength – 4hrs. => 3 N /mm 2 , 7 da ys =2 0 N/mm 2 , 28 days = 35N/mm2, Flexural strength – 7 days = 3N/mm2, 28 days = 7N/ mm2, Specific Gravity of 1.2 gms / ltr. In India, the Chowgule Construction Technologies range of products has been introduced over the past decade. The company is respected for its professionalism in our primary markets of Maharashtra, Goa, Tamil Nadu, Andhra, Karnataka and Kerala. It has achieved excellent results in complicated cases to the fullest satisfaction of our customers. Chowgule Construction Technologies Private Limited have specialized in waterproofing and concrete repair products for over a decade now. CCT is a part of the 97-year-old Chowgule Group of companies, which has its presence in shipping, logistics, and automotives in addition to construction chemicals. Chowgule Construction Technologies is in collaboration with KAU B I T A k t i e n g e s e l l s c h a f t f o r waterproofing and repair products, Schedetal AG for ECB and TPO membranes, OttoChemie for sealants and ABP for Epoxy and PU-based floor coatings. We are trusted by leading architects, consultants and developers in our areas of operations.

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Fire Shutter

Intelligent Shutters from Gandhi Automations

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onstructed of galvanized or stainless steel in a variety of gauges, slat designs and finishes for unsurpassed strength, durability and style. Wide ranges of styles meets or exceed industry fire safety testing standards including UL, FM and ULC. The doors are also compliant with all NFPA-80 standards. Door closes automatically under

governor control after separation of fuse link. UL-listed brush –type smoke gaskets satisfy smoke retardation requirements. Additional safety options include the fire SentinelTM time-delay release device photoelectric or ionization-type smoke detectors, with or without heat detector. Additionally available uninterruptible power supply for use with motor-

operated doors allows door closure by central alarm or smoke detector under motor power.

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E.Scape

Karnataka to Declare Results of

Solar Project Auctions

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arnataka, a South Indian State, is geared up to announce the winners of its solar power plants auction, under the supervision of KREDL (Karnataka Renewable Energy Development Ltd), a state-run agency. In a recent interview held in Chennai, the Managing Director of KREDL, N S Prasanna Kumar stated that the results of the state's first ever auction to grant contracts for solar projects will be announced in the coming week. The agency stated that the participants including Tata Power, Kiran Energy Solar Power Pvt, Welspun Group and Jindal Aluminium Ltd had submitted bids in December last year for 50 MW of photovoltaic capacity. Atria Power Corp and Sunborne Energy LLC, supported by billionaire Vinod Khosla had submitted bids for 30 MW solar-thermal projects. There was a delay in opening the bids as a legal problem surfaced following the agency's failure to conform with a rule entailing government bodies to use online procurement systems to award contracts. (Source: Bloomberg Pic Courtesy: http://weblog.greenpeace.org)

'THE SHOWCASE' Qatar's Gorgeous Stadium for the 2022 FIFA World Cup

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fter its successful bid in 2010 to host the 2022 FIFA World Cup, Qatar made ingenious plans to design solar-powered arenas that will not only exude outstanding architectural ingenuity, but will also be capable of sheltering against the summer heat. Among these, 'The Showcase' designed by Arup Associates is a net-zero stadium that took just four months for completion. With a capacity of 500 seats with under-side cooling, the arena's roof can be retracted and its photovoltaic solar panels supply to the grid when it is not being used. According to Architecture World News, oil-rich Qatar can easily excel in its sustainable design, defying former misconceptions that desert regions cannot host huge sporting events. The Showcase merges passive design with innovative energy-saving technology and comfortable architecture. It uses Fresnel parabolic mirrors to provide thermal cooling. Owing to the enormity of the multitude that throng the world's biggest sporting event, host nations give heed to environmental concerns, besides exhibiting path-breaking designs in their sports centers. South Africa, which hosted the 2010 World Cup created a range of eco-friendly arenas. Brazil, the 2014 World Cup host is set to create green renovation in a hotel, along with incorporating green trends in new constructions. Russia, the 2018 World Cup host is set to build a high-speed rail system. (Source and Picture Courtesy: Inhabitat)

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iverpool Department Store is an ultra-modern structure located in Interlomas, a traffic-heavy region outside Mexico City. The designer Rojkind Arquitectos has incorporated innovative elements to the circular shopping center, so as to create cultural and relaxation sites in the humdrum region. The store's silver fascia has a unique sheen that matches the quick-paced traffic around it. Nestled in the junction of multiple highways and overpasses, the store's double-layer façade has been fabricated with 3D models. The spectacular stainless steel covering on the outer layer serves to shelter the visitors from the surrounding traffic bustle, providing a tranquil space amidst the commotion in one of the busiest regions in the suburbs. Perforations in the silver layer allow infiltration of sunlight during the day. The three-story atrium of the Blade-Runner style structure brings light to the interior. At night the space between the two layers is filled with a wall of light, allowing colorful reflections on the steel fascia. Apart from community balconies, the structure has a roof garden that brings the much needed green touch to the area. (Source and Pic Courtesy: Inhabitat)

ASwankyBldeRurStyleDparmnoiMxcC StyleDparmno inMexcoCty

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The Masterbuilder_March 2012_Formwork and Tunneling Special

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