A PRESENTATION ON
“SELF COMPACTING CONCRETE Presented By Suhas Lahoti (G06145) Rohit Parsewar(G06156) Abhijit Pawar (G06158)
INTRODUCTION By the early 1990's, Japan has developed and used SCC.
Self
compacted concrete is highly engineered concrete with much higher fluidity without segregation and is capable of filling every corner of formwork under its self weight . Thus
SCC eliminates the vibration for the compaction of concrete without affecting its engineering properties. As
of the year year 2000, SCC used used for prefabricated for prefabricated products (precast members) and ready-mixed concrete (cast-in-place) (cast-in-place) in the Japan, USA, etc….
Development of SCC
In 1983, the problem of the durability of the concrete structures was a major topic of interest in Japan.
The creation of durable concrete structures adequate compaction by skilled workers. workers .
Solution for the achievement of durable concrete structures independent of the quality construction work is the use of SCC.. SCC
The necessity of this type of concrete was proposed by Okamura in 1986. 1986.
Studies to develop SCC have been carried out by Ozawa and Maekawa at the university of Tokyo.
Present-day SCC can be advanced construction material
classified
requires
as
an
The Important Properties • Self-compactability • Avoidance of bleeding and segregation • Low shrinkage • Low permeability • Strength as needed
What’s Different? • Segregation resistance from mortar viscosity & not due to aggregate grading. • Workability content.
through
admixtures,
not
• Self compacting due to own weight and not vibrators.
water
What is the secret? Paste Viscosity! Attained by one of three means: • High cement content • High content of Fly Ash, Silica Fume etc • Use of Viscosity Modifying Admixture Also low water content using HRWR
Basic requirements For successful casting of SCC : A.Excellent deformability 1. Increase deformability of paste by a) use of HRWR b) balanced water 2. Reduce inter-particle friction by a) low coarse aggregate volume ( high paste volume)
Continued…. B. Good Stability 1. Reduce separation of solids by a) limiting aggregate content b) increasing cohesion and viscosity 2. Minimize bleeding (free water) by a) low water content b) superplastisizers
Continued…. C. Low risk of blockage by: 1. Enhanced cohesiveness 2.Sufficient spacing between reinforcement and coarse aggregate
Benefits of SCC For Contractors: • Reduced vibration effort and noise during placing. • Ability to fill complex forms with limited accessibility. • More uniform distribution in areas of closely bunched reinforcement. • Rapid pumping of concrete. • Uniform and compact surface. • Less surface voids and need for rubbing and patching. • Improved aesthetics of flatwork for less effort.
Benefits of SCC For Ready-Mix Producers:
Better perception from customers by offering a technically advanced, higher value concrete mixture.
• Offers a product that saves customers time and money. • More efficient use of mixing equipment and delivery. • Can easily expand variety of products offered without adding more equipment. • Improved aesthetics of final product.
Benefits of SCC For Cast-in Place Fabricators: • Allows easier quality control. • Easier to achieve qualities of an optimally designed mix. • Can better guarantee properties due to tight quality control. • Faster slump loss means concrete is ready for steam-curing quicker.
limitations of SCC • Limited bleeding characteristics and plastic shrinkage may cause if not properly protected and cured. • Higher admixtures content can also lead to plastic shrinkage if not properly cured. • SCC requires a higher level of quality control than conventional slump concrete. Key items to monitor are: • Coarse and fine aggregate grading • Coarse aggregate void volume • Aggregate moistures
Technical advantages of SCC • Simple even in complicated formwork and tight reinforcement. • Higher installation performance since no compaction work is necessary. • Reduced construction times, especially at large construction sites • Reduced noise pollution since vibrators are not necessary. • Higher and more homogenous concrete quality across the entire concrete cross-section, especially around the reinforcement • Improved concrete surfaces (visible concrete quality) • Typically higher early strength of the concrete so that formwork removal can be performed more quickly.
Cost criteria •
The increased cost of the concrete of SCC balances against labor savings and aesthetic benefits. • Contractors, producers and owners are under great pressure to produce better quality construction at lower costs of labor, materials and equipment. Reduced in-place cost: • SCC can increase the speed of construction, improve surface finish and thus reduce repair, patching costs & reduce maintenance costs on equipment. Reduced labor costs: • Reduces labor demands of skilled labour for quality concrete works. Improved work environment and safety: • minimizing noise exposures & also It reduces fall hazards, as workers do not have to stand on forms to consolidate concrete. Improved aesthetics • Provides finished surfaces thus reduces the finishing costs .
Factors affecting SCC 1. Aggregate volume 2. Size distribution & shape of aggregate 3. Ratio between fine and coarse aggregate 4. Density of paste of aggregate 5. Surface property of aggregate 6. Void content of aggregate
Material required • CEMENT • FINE AGGREGATE • COARSE AGGREGATE • FLYASH • WATER • HIGH RANGE WATER RETARDERS • VISCOSITY MODIFYING ADMIXTURES
Principals of SCC mix design Small size & limited coarse agg.
HRWR’s
Viscosity Modifying agents
Mineral Admixtures
Reduction of internal stress causing blockages
Increase Paste flow
Increase paste viscosity to prevent segregation
Low heat of hydration, Enhances Stability
TYPES OF SCC There are three ways in which scc can be made • POWDER TYPE – Scc is made by increasing the powder content • VMA TYPE – Scc is made by using viscosity modifying admixture • COMBINED TYPE – Scc is made by increasing the powder content and adding VMA
MIX PROPORTIONS PARTICULARS
UNITS
M60
POWDER TYPE
VMA TYPE
COMBINED TYPE
COARSE AGGREGATE
Kg/m3
1108.13
1108.13
1108.13
1108.13
FINE AGGREGATE
Kg/m3
683.24
683.24
683.24
683.24
CEMENT
Kg/m3
504.21
504.21
504.21
504.21
FLY ASH
% of cement
0
10
0
5
WATER
Kg/m3
141.61
141.61
141.61
141.61
HRWR
l/m3
4.668
4.668
4.668
4.668
0
0
0.8
0.4
VMA
l/100kg of cement
HIGH RANGE WATER RETARDERS (HRWR) SUPERPLASTICIZER • Super plasticizer (VARAPLAST PC 100) is used as high range water retarder. • Super plasticizing action of varaplast pc100 is different than conventional super plasticizers based on – sulfonated melamine formaldehyde condensate, – sulfonated naphthalene formaldehyde condensate
which create electrostatic repulsion of particles. • Varaplast pc 100 is free from chlorides and complies with ASTM C494 G (retarding super plasticizer).
HRWR CONTD… TYPICAL PROPERTIES • Calcium chloride content: Nil • Specific gravity: 1.08 at 20 C • Air entrainment: Less than 1% additional air is entrained • Setting time: 1-4 hours retardation depending on dosage and climatic conditions • Chloride content: Nil
Commonly used Superplasticizers • • • • • • • • • •
Modified Lignosulfonates(MLS). Sulfonated Melamine Formaldehyde (SMF) Sulfonated Naphthalene Formaldehyde(SNF) Acrylic Polymer based(AP) Coplymer of Carboxilic Acrylic Acid with Acrylic Ester(CAE) Cross Linked Acrylic Ploymer(CLAP) Polycarboxylatethers(PCE) Multicarboxylatethers(MCE) Polyacrylates
VISCOSITY MODIFYING ADMIXTURE (VMA) • VMA is an admixture used for enhancing the viscosity and rheological properties (flow of fluids). • Polyethylen glycol and biopolymers are combined and used as VMA
Flow tests of self compacted concrete
U box test
Slum test
Test result in brief
Limiting test Values
Test Result in Brief
CASE STUDIES
CASE-STUDIES :Current condition on application of self compacting concrete in Japan: After
the development of the prototype of self-compacting concrete at the University of Tokyo, intensive research was begun in many places, especially in the research institutes of large construction companies. As a result, self-compacting concrete has been used in many practical structures.
The first application of self-compacting concrete was in a building in June 1990. Self-compacting concrete was then used in the towers of a prestressed concrete cable-stayed Shin-Kiba Ohashi bridge in 1991. Lightweight selfcompacting concrete was used in the main girder of a cable-stayed bridge in 1992.
1.Shin-Kiba Ohashi bridge in 1991 in Tokyo :
Case study continued….
The use of self-compacting concrete in actual structures has gradually increased. Self-compacting concrete has been successfully used in France, Denmark, Netherlands,Germany,USA and UK, apart from Japan.
A typical application example of Self-compacting concrete is the two anchorages of Akashi-Kaikyo (Straits) Bridge opened in April 1998, a suspension bridge with the longest span in the world (1,991 meters) . The volume of the cast concrete in the two ahchorages amounted to 290,000 m3.
2.Akashi-Kaikyo suspension bridge in Japan
Case study continued…. • Self-compacting concrete was used for the wall of a large LNG tank belonging to the Osaka Gas Company, whose concrete casting was completed in June 1998. • The volume of the self compacting concrete used in the tank amounted to 12,000 m3. The adoption of self-compacting concrete means that , (1) the number of lots decreases from 14 to 10, as the height of one lot of concrete casting was increased. (2) the number of concrete workers was reduced from 150 to 50. (3) the construction period of the structure decreased from 22 months to18 months.
3.LNG tank belonging to the Osaka Gas Company, Japan:
4.SCC for Rafts & Retaining Walls for Kesar Solitaire,Navi Mumbai :
4.SCC for Rafts & Retaining Walls for Kesar Solitaire,Navi Mumbai • The Kesar Solitaire is a prestigious project being developed by M/s. Kesar Group, when completed would be a landmark on the Palm Beach Road in Navi Mumbai. This commercial complex is situated just next to the creek and the water table is about 1 meter below the ground. On examining the water, it was found to be highly saline and the chloride content in water was more than 7000 ppm. Another issue at the site was the upcoming monsoons, the basement needed to be completed before the start of the monsoons, which otherwise would have flooded the site. It was therefore decided to go for an M 40 grade SCC for the triple basement structure, which was 10 meters below the ground level.
continued…. • The SCC mix was designed with “Corniche SF” brand Silica Fume to take care of the chloride ion permeability of the structure due to the saline water table. An RCPT value of less than 1000 coulombs according to ASTM C 1202 and water permeability of max 50 mm according to DIN 1048 was specified, so as to ensure the durability of the raft concrete. The mix actually contained higher binder content and therefore the water demand was high. To ensure thorough dispersion of silica fume and fly ash, a PCE based admixture was used.
continued…. • The thickness of the wall was 300 mm and after erecting the form work it was a challenge by itself to place and vibrate the concrete. It was therefore decided to use M 40 grade SCC so that even 3 meter pour (free fall) of concrete is possible. The use of SCC in retaining walls actually helped in achieving a homogeneous concrete void of any honey combs. The strengths achieved were more than 50 MPa at 28 days as the water binder ratio was maintained at 0.33
• The mix design and the strengths achieved are given here : Materials OPC 53 grade Fly ash "Comiche SF" silica fume Binder 20mm Agg 10mm Agg River Sand Crusher dust Water Glenium sky 584 Glenium stream 2 W/c Ratio Slump flow after 60 min
Kgs/M3 400 175 20 595 334 413 396 432 196 0.80% 0.15% 0.33 650 min
v Funnel after 60 min 3 Days 7 Days 28 Days
10 seconds 27 Mpa 42MPa 54MPa
INDIAN SCENARIO OF SCC • Current Indian scenario in construction shows increased construction of large and complex structures, which often leads to difficult concreting conditions. • In India, during last few years, attempts were made in the laboratories and in the field to develop and use SCC. • Some efforts have been made in Delhi Metro Projects in association with L&T a large scale SCC for dome construction and tunnel lining, column casting, etc, are used to attain 35 MPa strength. • The knowledge of SCC has moved from domain of research to application. But in India, this knowledge is to be widespread.
EXAMPLE FOR SCC STRUCTURES
TUNNEL LINING DMRL
EXAMPLE FOR SCC STRUCTURES
DOME CONSTRUCTION IN CENTRAL STATION IN
Different Codes used For SCC • Annexure J of IS 456 as Amendment no 3. • BS EN 206-9:2010 • EN 197-1 Cement-Composition, specifications and conformity criteria • EN 206-1 Concrete – Specification, performance, production, and conformity • EN 450 Fly ash for concrete – Definitions, requirements and quality control • EN 934-2 Admixtures for concrete – Definitions and requirements • EN 1008 Mixing water for concrete • EN 12350-1 Testing fresh concrete: Part 1: Sampling • EN 12350-2 Testing fresh concrete: Part 2: Slump test • EN 12620 Aggregates for concrete
CONCLUSION • A new technology for eliminating vibrators in heavy structure where vibration is impossible. • We conducted different fresh concrete test and also conducted hardened concrete test. • Adding viscosity modifying admixture (polyethylene glycol) and fly ash combination is very much suitable for self compaction is high strength concrete. • Advantage with respect to sound pollution. • Ideal for concrete parts with complicated shapes and elements with high quality visible concrete.
