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EARTHQUAKE RESISTANT BUILDINGS WITH HOLLOW INTERLOCKING BLOCKS

TRAINING MANUAL FOR ARCHITECTS AND ENGINEERS

 Auroshilpam, Auroville 605 101, TN INDIA Email: [email protected] [email protected]

Tel: +91 (0) 413 – 262 3064 / 262 3330

Fax: +91 (0) 413 – 262 2886 Website: www.earth-auroville.com

EARTHQUAKE RESISTANT BUILDINGS WITH HOLLOW INTERLOCKING BLOCKS TRAINING MANUAL FOR ARCHITECTS AND ENGINEERS

Author: Satprem Maïni Auroville August 2001 Revised April 2005 43 pages AUROVILLE EARTH INSTITUTE Ref: TM. 03

Humanity as a whole No rights reserved! All parts of this publication may be reproduced, by any means, without the written permission of the author. Feel free to disseminate this information anywhere!

CONTENT

FOREWORD

I

PREFATORY NOTE

ii

PART ONE – EARTHQUAKES AND STRUCTURES

1 3 5 9

1.1 Earthquakes 1.2 Earthquake effects on a structure 1.3 Principles for earthquake resistance PART TWO – SOIL AND STABILISATION

2.1 The raw material 2.2 Principles for soil identification 2.3 Soil stabilisation 2.4 Stabilisation calculation 2.5 Improving and stabilising soils 2.6 Testing soils PART THREE – COMPRESSED STABILISED EARTH BLOCKS

3.1 Basic data on CSEB 3.2 Sustainability and environmental friendliness of CSEB 3.3 Hollow interlocking blocks for earthquake resistance 3.4 Blockyard organisation 3.5 Quality control 3.6 Cost analysis 3.7 Economic feasibility study

11 12 13 13 14 16 17 19 20 20 20 22 22 25 26

4.1 Basic design guidelines for CSEB 4.2 Basic design guidelines for earthquake resistance r esistance 4.3 Design guidelines for hollow interlocking blocks 4.4 Laying Hollow Interlocking CSEB 4.5 Bonds with the blocks 245 4.6 Bonds with the blocks 295 4.7 Example of plan with the block 245 4.8 Example of plan with the block 295

29 30 32 35 37 39 40 41 42

SELECTED BIBLIOGRAPHY

43

PART FOUR – DESIGN AND MASONRY

PREFATORY NOTE This manual presents the basics on earthquake mechanisms, the various stages of a manual production line using the AURAM equipment for Hollow Interlocking CSEB. It gives also the guidelines for earthquake resistant buildings, using the technologies developed by the Auroville Earth Institute for earthquake resistance. These technologies are based on stabilised earth for the foundations, plinth and walls. The system used for   the load bearing walls is masonry built with hollow interlocking compressed stabilised earth blocks, which are reinforced with reinforced cement concrete (RCC). The technology has government approval: - The Government of Gujarat, India, (GSDMA) as a suitable construction method for the rehabilitation of the zones affected by the 2001 earthquake in Kutch district. It is allowed to build up to 2 floors. - The Government of Iran (Housing Research Centre) as a suitable construction method for the rehabilitation of the zones affected by the 2003 earthquake of Bam. It is allowed to build up to 3 floors (8m high). - The Government of Tamil Nadu, India, (Relief and Rehabilitation) as a suitable construction method for   the rehabilitation of the zones affected by the the 2004 tsunami of Indonesia.

ii

PART ONE

EARTHQUAKES AND STRUCTURES

1

1.1 EARTHQUAKES ¾Origin

of earthquakes

The earth was a single land about two hundred million years ago. This land split progressively over a long period of  time and it gave tectonic plates. Theses tectonic plates are still moving and earthquakes are the result of these movements. Therefore, the continents of  the earth are like several pieces of a crust – the tectonic plates, which are floating on a viscous mass – the magma. The latter is like a thick liquid composed of rocks in fusion. Under various circumstances, these  tectonic plates are still moving, very slowly, towards each other or away from each other. These movements generate a lot of friction, which generate tensions and compressions in the earths crust. This friction is like energy, which gets stored in the deepest strata of the ground. Earthquakes happen when the ground cannot accumulate anymore this energy, which is then released with violence on the surface of the globe. The original focus of the earthquake is called the hypocentre. It lies deep into  the ground. The geographical point on  the surface, which is vertical to the focus, is called the epicentre.

TECTONIC PLATES 2

¾Seism types

Seisms can be of various natures. The most frequent ones are due to the movement of tectonic plates. Earthquakes can have other natures: volcanic or caving in. - Tectonic earthquakes are the most devastating ones. The energy stored, due to the slow friction during a very long period of time, is tremendous. The earth crust is plastic enough to store this energy for a long  time and without elastic failure. When the earth crust cannot store anymore this energy, it is released in  the form of a tectonic earthquake. - Volcanic earthquakes are due to the movement of magma under the earth crust. Its causes can be a local push of magma, which breaks the earth crust. A caving in of an underground cavity, which was created by a magma movement, can also be its origin. The other origin of volcanic earthquakes is volcanic explosions and eruptions. Volcanic earthquakes are not much devastating. - Caving in earthquakes are quite exceptional. The caving in of the ceiling of underground cavities creates  them. They can happen everywhere on the globe and they are not very powerful and devastating. ¾Seismic waves

The seism focus generates spherical pulses, which propagate like concentric waves. They are called body waves. These initial waves have a longitudinal action and they are called primary or P waves. These waves induce second body waves, S waves. When P & S waves reach the surface they create 2 other waves: Love & Rayleigh waves.

S waves

P Waves

Their manifestation creates a change in volume They also called shear or transversal waves and and generates compression and dilatation of the  they are very destructives. The soil oscillates ground. Their velocity is high: 5 to 8 Km/s. vertically and perpendicularly to their direction. Their velocity is lower than P waves: 3 to 5 Km/s.

L waves

R waves

(Love waves) They are also transversal ones, like S waves. The soil oscillates horizontally and perpendicularly to  their direction. Their velocity is like S waves.

(Rayleigh waves) The soil oscillates in an elliptical movement, counter clockwise to their direction. Their velocity is a little lower than S waves.

3

¾Measure

of seism

Two scales measure earthquakes: the Richter scale and the Mercalli scale. - The Richter scale gives a quantitative measure of earthquakes. It defines the magnitude of an earthquake,

which is the amount of energy released on the surface. The Richter scale is logarithmic: each whole number increase in magnitude represents a ten-fold increase in the measured amplitude of the seism. This scale has no upper limit, but the largest known shocks have had magnitudes up to 8.8 to 8.9. The earthquake of January 2001 in Gujarat was measured at 6.9 by the Indian seismographs and at 7.8 by the Japanese and American seismographs. - The Mercalli scale assesses the effects of an earthquake. It defines the intensity of the earthquake, which

is expressed from 1 to 12. The intensity and thus the effect of the seism are related to the distance from  the epicentre. It is based on more subjective effects, like movement of furniture, extents of damages to structures, modification of the landscape, etc. ¾Earthquake effect

Earthquakes don’t directly kill people. Ground shaking destroys infrastructure and buildings and hence, it is of a material nature. Death of people is occurred by the collapse of buildings in which they live. Therefore,  the real cause of life’s loss is badly built or un-appropriate constructions, which instantly collapse without warning. ¾Ground

motion during an earthquake

As we have seen previous page, the hypocentre of an earthquake generates various types of waves. When  they reach the surface, the ground shakes everywhere horizontally and vertically especially near the epicentre. The motions are always reversible and this implies that buildings vibrate in all directions and in a very irregular manner due to the inertia of their masses. ¾Seism prediction

It is not possible to predict earthquakes. Parameters involved and the absence of sufficient data makes it impossible to foresee, where, when and with which magnitude would strike an earthquake. ¾Earthquake prevention

If it is not possible to predict earthquakes, it is possible to prevent major damages and most of life’s losses. India is divided in five zones and there are several Indian standards, which defines building codes for  earthquake resistance. The design of every engineered or non-engineered building must follow it. Further, the construction must be well built, that means by people who should follow the state of the art in construction, or at least the basics of masonry, and who are conscious of their responsibility in the execution of a building, which must resist an earthquake. The prevention of earthquakes is based on the possibility of buildings to resist earthquakes without sudden collapse. ¾Seismic zones

India has been mapped in 5 zones, according to the risk of earthquakes: zone 5 has the greatest risk for  earthquakes (See IS 1893: 1984). These zones are mainly based on the Mercalli scale. They are related to: - Intensity and magnitude of past earthquakes - Probability of earthquakes - Nature of the ground and soil-foundation system - Risk occurred because of the density of population and/or buildings

4

¾Seismic

zones of India

1.2 EARTHQUAKE EFFECTS ON A STRUCTURE Structural elements, such as walls, columns and beams, are only bearing the weight of the building and the live load under normal conditions: mostly compression forces for the walls and columns, and vertical bending for the beams. Under dynamic load, they also have to withstand horizontal bending and shear  forces, and extra vertical compression forces. ¾Failure mechanism of walls

GROUND MOTION IN THE WALL PLANE

GROUND MOTION PERPENDICULAR TO THE WALL

5

¾Typical

damages in a masonry building

1: Diagonal shear crack of piers 7: Plaster peeling off 2: Horizontal shear crack of long pier  8: Crushing of weak masonry under vertical ground motion 3: Bending cracks at feet and lintels 9: Damage of corner eaves under vertical ground motion 4: Bending crack of wall (bad corner bond) 10: Badly anchored roof, pulled out by vertical ground motion 5: Bending crack of spandrel 11: Falling of tiles from the roof eave 6: Bending crack of gable 12: Damage of tiles roof with shear (roof not braced)

Khavda

Ludiya

Badly built buildings

Adobe buildings, which withstood the earthquake of Gujarat 6

Near Bhuj

Ludiya

Bad bonds and no “through stones”

Typical shear crack in a pier

Crack due to bending & shear

Shear crack

Shear crack in filler wall

Bending cracks at door

Prag Mahal – Bhuj, Built at the XIXth Century 7

Overturning of parapet wall

Well built = Minor damages

Failure due to collapse of walls or columns

Failure due to collapse of column

Stirrups too weak

No steel angle in the corner

Failure due to shear & bending

Steel bars not centred

Not enough gap between 2 buildings 8

Stirrups too weak 

No anchorage in the column

1.3 PRINCIPLES FOR EARTHQUAKE RESISTANCE Though hi-tech technologies exist in Japan and USA, it is not economically possible to build earthquake proof buildings, especially for low-income groups and small projects. But it is possible to build easily earthquake resistant buildings, without much extra cost, and which would not collapse suddenly without warning. Any new building which is located in the zones 3, 4, 5 must be designed to resist earthquakes. For projects, like houses, this can be satisfied by a well built construction, which follows all basics of masonry guidelines, like bond pattern, mortar quality, brick or stone laying, etc. In the case of the last earthquake of January 2001 in Gujarat, some traditional houses made of adobes or stones withstood very well the seism violence. They were simply well designed and well built.

An earthquake resistant building is able to accumulate a lot of energy without major failure. It will swing and sway and it might be damaged. But it would not collapse before giving very visible signs. Therefore, people would be able to leave the building before it would collapse. An earthquake resistant building, which has been damaged, could most of the time be repaired. ¾Terminology

- Band or ring beam – A reinforced concrete or reinforced brick runner, which ties all the walls together. It

imparts the horizontal bending of the walls. - Box system – A structure made of a load bearing masonry wall without a space frame. The walls, acting as shear walls, are resisting the horizontal forces. - Brittleness – The possibility of a structure to crack and collapse easily. It is arising either from the use of brittle materials or from a wrong design. The opposite of brittleness is ductility. - Centre of gravity – The point through which the resultant of the masses of a system acts. It corresponds  to the centre of gravity of the plan. - Centre of rigidity – The point through which the resultant of the restoring forces of a system acts. It is the rotation point of the structure and it is related to the masses of the vertical parts of a building. - Ductility – The ability of a building to bend, sway and deform by a large amount without collapse. The building may crack and get damaged in some parts, but it would not collapse. The opposite of ductility is brittleness. A building built with brittle materials can be made ductile with a proper design and with the incorporation of various reinforcements. - Plasticity – The property of a material, and especially a soil, to be submitted to deformation without elastic failure. A humid soil is quite plastic and can absorb a lot of energy before breaking. A dry soil will be less plastic, but will still be able to absorb more energy than stones or fired bricks before failing. - Shear wall – A wall, which resists lateral forces in its own plane. Shear walls are structurally linked with other cross walls and with floors and roofs, which acts as diaphragms. Wide piers and buttresses are considered as shear walls. - Vertical tie – A RCC reinforced member, which ties the various ring beams, from plinth to roof. ¾Site location

The nature and stability of the natural ground will affect the buildings. It is not always or rarely possible to select a site for its characteristics for earthquake resistance. Spontaneous human settlements have another  approach to select a place. Very loose sands and sensitive clay should generally be avoided. These two types of soils are liable to be destroyed by the earthquake and they will loose their original structure. Especially, if soils without cohesion get saturated with water they might loose their shear resistance and get liquefied. ¾Design

and construction quality

Major damages and collapse are, in most the cases, attributed to wrong design and particularly to very poor  quality constructions made by bad workmanship. Much less damaged would occur if masons, contractors, engineers and architects were always following the basics of masonry guidelines such as: ¾Simple and appropriate design ¾ Proper bonds with appropriate and well laid mortar  ¾ Etc. ¾Good detailing in general ¾ Good overlap of steel bars and good cover with concrete 9

Khavda

Well built buildings which resisted the earthquake in Gujarat

Near Bhuj

¾Box system and reinforced masonry

The structure should be done in such a way that the walls are bracing each other to prevent bending moment. Walls should also be designed as shear walls to resist the lateral forces in their plane. This means  that openings should be small, rather centred and not too close from corners. Reinforcing the masonry should not be a way to improve a wrong design. It would rather be a means to add more strength to the building.

10

PART TWO

SOIL AND STABILISATION

11

2.1 THE RAW MATERIAL ¾Definition

Soil is the result of the transformation of the underlying rock under the influence of a range of physical, chemical and biological processes related to biological and climatic conditions and to animal and plant life. ¾Fundamental properties

- Granularity or texture = Grain size distribution of a soil. (Percentage by weight of the different grain size) - Compressibility

= Ability to be compressed to a maximum. It is related to the energy of compaction and the moisture content = OMC (OMC = Optimum Moisture Content = percentage by weight of water)

- Plasticity

= Property of a soil to be submitted to deformation without elastic failure.

- Cohesion

= Capacity of its grains to remain together.

¾Composition

of a soil = It is an earth concrete

- Gaseous components - Liquid components - Solid components

Cement is the binder for concrete. In a soil, the binder is silt & clay. Thus, it is like a concrete, but silt & clay are not stable under water. Therefore they should be stabilised, to maintain some strength when the blocks get wet. The grain size classification adopted by a large number of laboratories is based on the ASTM-AFNOR standards: Pebbles

Gravel

Sand

Silt

Clay

200 to 20 mm

20 to 2 mm

2 to 0.06 mm

0.06 to 0.002 mm

0.002 to 0 mm

For compressed stabilised earth bocks, pebbles should be removed. ¾Good soil for compressed stabilised earth

blocks

It is much more sandy than clayey.

It has a particular proportion of the four components: gravel, sand, silt and clay (Pebbles are screened). Gravel

Sand

Silt

Clay

15 %

50 %

15 %

20 %

¾Typical soils

According to the percentage of the four components, the soil will be classified as: Gravely soil – Sandy soil – Silty soil – Clay soil. A more accurate classification will need some subtleties, i.e.: Silty sand soil = Soil mainly sandy with an influent proportion of silt. Sandy silt soil = Soil mainly silty with an influent proportion of sand. ¾Structure

of a soil

It is how the grains are assembled. There are 3 structures: = A lot of voids (i.e. gravel) - Granular structure - Fragmented structure = Discontinuous (i.e. gravel and clay only) - Continuous structure = the best (i.e. the proportion of the best soil: see above) 12

2.2 PRINCIPLES FOR SOIL IDENTIFICATION ¾Sensitive analysis:

They follow the four fundamental properties of the earth. They can be practiced by anybody: = - The soil is dry / solid or humid: look and touch it to examine the - Granularity percentage and size of the four components. = - Add a little water to get a moist soil and compress it by hand to try to - Compressibility make ball. = - Add more water and make a ball. - Plasticity - Try to pull the ball like rubber elastic. - Stick a knife into it and cut it with the knife. - Water absorption in a small print done with the thumb in the ball. = - Add much more water to loose the cohesion and to wash the hands. - Cohesion The humus content must be checked: = - An important test is to check the humus, which may give problems with the - Humus Content stabilization: take a moist soil and smell it. The aim of this sensitive analysis is to find out in which categories goes the soil sample: Gravely, Sandy, Silty, Clayey or combined soil i.e. sandy clay. Then, according to this classification, one must look into the recommendations for stabilization and soil improvement. ¾Laboratory Tests

They follow the four fundamental properties of the earth, but they need special equipment: - Granularity = Grain size distribution (sieving + sedimentation). - Compressibility = Proctor for getting the OMC. = Atterbergs limits For example: Sand 0 < IP < 10 - Plasticity (LL, PL, IP) 0 < LL < 30 (SL, LS, LA, CA.) Silt 5 < IP < 25 20 < LL < 50 Clay 20 < IP 40 < LL = = 8 test (mortar < 2 mm) - Cohesion

2.3 SOIL STABILIZATION ¾Definition

It aims to stabilise under water the binders, which are the silts and clays, in order to obtain lasting properties and strength when the soil gets wet. ¾Procedures

PRINCIPLE

ACTIONS

-

Mechanical The soil is compacted.

Physical

The texture of the soil is corrected by adding or removing aggregates, which are inert materials.

Chemical

Processed products, which are active materials like chemicals, are added to the soil.

Density and mechanical strength are increased. The water resistance is increased. The permeability and porosity are decreased. The soil is sieved to remove the coarse particles. Different soils are mixed to get a better texture. Gravel or sand is added to reinforce the skeleton. Clay is added to bind better the grains.

- They help binding the grains of the earth.

13

¾6

Methods

Densification – Reinforcement – Cementation – Linkage – Imperviousness – Waterproofing DEFINITION

EXAMPLES

Densification

Create a dense medium, blocking pores & capillary

Reinforcement

Create an anisotropy network limiting movement

Cementation

Create an inert matrix opposing movement

Linkage

Create stable chemical bonds between clay and sand

Imperviousness

Surround every earth grain with a waterproof film

Waterproofing

- Compaction - Adding components - Mixing different soils - Straw - Fur  - Synthetic fibres - Cement - Fly ash - Lime

- Bitumen & Resins - Various chemicals Avoid the water absorption and adsorption by the surface - Paints, plaster * - White wash Note: * Avoid bitumen and synthetic paints or plasters for earth walls.

¾Variety of stabilisers

Fibres (natural or synthetic), cement, lime, fly ash, natural products (straw, fur, blood, juice of plants, latex, etc.), resins, and synthetic products. ¾Suitability

of stabilisers and their percentage for earthquake resistant CSEB SUITABILITY MINIMUM % AVERAGE %

Cement

Mostly for sandy soil

5%

7%

Lime

Mostly for clayey soil

5%

8%

MAXIMUM %

No technical maximum Economic maximum: 9 - 10 % 10%

2.4 STABILISATION CALCULATION ¾Aim

It is to define the percentage of stabiliser and the quantities of the different components. ¾Principle

The calculations are always done by weight of dry material. As it is impossible to measure weights on site,  they have to be transformed into volumes. Then, the dry density (δ) is needed. ¾Formulas

They can be used for all stabilisers, but we give here the example with cement. The aggregates are soil or  (soil + sand) or (soil + gravel), etc. The total percentage of different aggregates is always 100 % as the binder is not yet included. 1. Density ( ) 2. Theoretical weight aggregates 3. Theoretical volume aggregates (Do it for each aggregate) 4. Exact % cement * Total weight

= Weight per litre = Weight cement wanted x (100 - % cement wanted) % Cement wanted = Theoretical weight aggregates x % particular aggregate Density particular aggregate x 100 = Weight cement wanted x 100 Total weight* = (Approximated volume of each aggregate x its density) + cement weight

14

¾How

to do? 1. Define the parameters : -Percentage and weight of cement, which is wanted. (Cement quantity should be calculated for not more than 250 litres of aggregates. It often corresponds to not more than 1/3 of a bag per mix). -Percentage of sand, gravel or else, which might need to be added. -Volume in litres of the containers available (Wheelbarrows, buckets, etc). 2. Density check up : Check the dry densities = weight of 1 litre (Formula 1). 3. Weight of aggregates : Calculate the weight of aggregates, required to get the percentage of cement wanted (Formula 2). 4. Transformation : Transform the weight of aggregates into volume for each aggregate (Formula 3). 5. Approximation : Approximate the volume of aggregates, according to the containers, which

6. Exact % cement 7. Selection 8. Adaptation

are available on site: to get practical and easy measurements for the site. Always keep in mind for this approximation that the transportation should be as easy and as fast as possible. : Calculate the exact percentage of cement, according to the weight of approximated aggregates (Formula 4). : Select the result if it is within a tolerance of 3% maximum from the percentage of cement wanted (i.e. 4.85 to 5.15 instead of 5%). : If the result is not satisfactory, redo all the process with another  approximation for the volume or with other parameters.

¾Practical grid

This grid is valid only for one soil with one stabiliser (cement) so as to get ± 7% cement stabilisation. Soil density ( )

Volume of soil (Litres)

Weight of cement (Kg)

1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60

180 180 165 165 150 150 150 135 135

16.6 = 1/3 bag 16.6 = 1/3 bag 16.6 = 1/3 bag 16.6 = 1/3 bag 16.6 = 1/3 bag 16.6 = 1/3 bag 16.6 = 1/3 bag 16.6 = 1/3 bag 16.6 = 1/3 bag

Exact % of cement 7.13 6.87 7.18 6.93 7.32 7.09 6.87 7.35 7.13

¾Example 1

1. Parameters: - 7% cement wanted and 1/3 bag (16.67 kg)

- 150 litres wheelbarrows + 15 litres buckets - 100% soil required (no sand added) - Dry density checked for the soil: δsoil = 1.35 2. Weight of aggregates (Formula 2): Soil = 16.67 x (100 – 7) = 221.47 kg

7 3. Volume of aggregates (Formula 3): Volume of soil = 221.47 x 100 = 164.05 Lt. 1.35 x 100 4. Approximation: According to the containers available and to transport easily the soil, we choose for the volume of soil: 1 wheelbarrow (150 Lt.) + 1 bucket (15 Lt.)= 165 Lt. 16.67 x 100 = 6.96% 5. Exact % of cement (Formula 4): % = (165 x 1.35) + 16.67 6. Selection: 6.96 is within the 3% tolerance (6.79 ≤ 6.96 ≤ 7.21) for the cement percentage and we select it. 7. Adaptation: Redoing all the process is not needed. 15

¾Example

2 1. Parameters: - 8% Cement wanted and 1/3 bag cement (16.67 kg)

- 100 Lt. wheelbarrows + 15 Lt. buckets - 70 % of soil and 30% of sand required - Dry density checked: δsoil = 1.2 and δ sand = 1.45 2. Weight of aggregates (Formula 2): Soil + Sand = 16.67 x (100 – 8) = 191.70 kg. 8 3. Volumes of aggregates (Formula 3): Volume of soil = 191.7 x 70 = 111.82 Lt. 1.2 x 100 Volume of sand = 191.7 x 30 = 39.66 Lt. 1.45 x 100 4. Approximation: According to the containers available and to transport easily soil and sand, we choose: Sand = 45 Lt. = 3 buckets of 15 Lt. Soil = 100 Lt. = 1 wheelbarrow of 100 Lt. 16.67 x 100 = 8.25% 5. Exact % of cement (Formula 4): % = (100 x 1.2) + (45 x 1.45) + 16.67 6. Selection: 8.25 is only 0.1% above the superior limit of the 3% tolerance (7.76 ≤ 8.25 8.24) for the cement percentage. As there is only 0.1% more, we can select it. 7. Adaptation: Redoing all the process is not needed .

2.5 IMPROVING AND STABILISING SOILS FOR EARTHQUAKE RESISTANT CSEB According to the original soil quality, adding materials like gravel or sand can improve easily the structure of  the soil. Note that adding clay is difficult, as it should be powered and this is quite hard to do on site with only manual means. Improvement can also be done by sieving the soil or by mixing different qualities of soil. Stabilising a soil will of course improve it a lot, but it should be done only after improving its structure. ¾Gravely Soil

- Sieving, with mesh size # 8 to 10 mm, is indispensable to remove coarse gravel. - A maximum of 15% to 20% by weight of gravel passing the screen will be allowed. - The maximum size for the gravel passing through the sieve will be ∅10 mm. - If the soil is too gravely, mix with it another soil, which is more clayey. - The minimum cement stabilisation will be 4% by weight, if the clay content is not less than 15 %. - The average cement stabilisation will be 6% by weight. ¾Sandy Soil - Sieving, with mesh size # 10 to 12 mm, is only required to loosen, aerate the soil and break up lumps. - Do not sieve in a very windy area, especially if the soil is dry, so as not to loose the fine clay. - The minimum cement stabilisation will be 5% by weight. - The average cement stabilisation will be 6-7% by weight, if the clay content is not less than 15%. ¾Silty Soil - A slight crushing might be required and sieving, with mesh size # 6 to 10 mm, is required. - Adding some coarse sand (10 to 20 %) might be needed to give more skeletons to the soil, only if the clay

content is not less than 20%. When the silt content is high (more than 25-30%) and the sand very fine (0.06  to 1mm), adding coarse sand and a clayey soil will improve the structure. - The minimum cement stabilisation will be 6% by weight. - The average cement stabilisation will be 7-8% by weight. ¾Clayey Soil

- Crushing might often be required and sieving, with mesh size # 6-10 mm, is required. - Adding a lot of sand (30 to 40 % ) is most the time needed to reduce the plasticity and to give some skeletons. - The minimum cement stabilization will be 7% by weight and the average cement stabilisation will be 8% . - Lime stabilisation can be used instead of cement. The minimum will be 8 % and the average will be 9% by

weight of lime. Then, the adjunction of sand will be reduced. - A combination of cement-lime stabilisation, can give good results.

For example: 3% cement + 5% lime + sand as needed. 16

2.6 TESTING SOILS ¾Sensitive

analysis and comments of four typical soils (gravely, sandy, silty, clayey), and a good soil

- Look and touch. - Add water to get a humid soil and smell it. - Try to compress the moist soil. - Add water and make a plastic ball. - Try to pull the ball like rubber elastic. - Stick a knife into it. - Cut the ball in two pieces with a knife.

- Absorption: do a print with the thumb in the plastic ball & fill it with water. - Wash your hands with water. ¾Comments

on the soil to be used ¾Sensitive analysis and comments of various soil qualities ¾Dry density check 

Measure it for the dry soil to be used. - Take 1.5 litre of loose humid soil. - Dry this sample. - Weight 1 litre of dry soil. - Redo 3 times this check. - Take the average for the dry density. ¾Testing

typical soils with a press

- Sensitive analysis on various soils. - Experimentation with the four typical soils and good soil with a press: Making 3 blocks of each soil quality. - The detailed results of the experimentation are given next page. ¾Behaviour

of typical soil with a press - The moisture is above the OMC (+ +) - A little water is needed for mixing (- -) - A little soil is needed to mould (- -) - A low compression ratio is required (- -) - Little influence of the moisture content on the penetrometre (-) Note: This last result is paradoxical but is due to the granular 

structure of the soil. - The moisture is above the OMC (+) - A little water is needed for mixing (-) - A little soil is needed to mould (-) - A low compression ratio is required (-) - Big influence of the moisture content on the penetrometre (+ +) - The moisture is below the OMC (-) - A lot of water is needed for mixing (+) - A lot of soil is needed to mould (+) - A high compression ratio is required (+) - Little influence of the moisture content on the penetrometre (-) - The moisture is below the OMC (- -) - A lot of water needed for mixing (+ +) - A lot of soil needed in the mould (+ +) - A high compression ratio is required (+ +) - Very little influence of the moisture content on the

penetrometre (- -) 17

GRAVELY SOIL

SANDY SOIL

SILTY SOIL

CLAYEY SOIL

M I X I N G

- Easy (+ +) - Difficult to get the OMC (-) - Little water is required (- -)

- Easy (+) - Difficult to get the OMC ( -) - Little water is required (-)

- Difficult (-) - Easy to get the OMC (+) - A lot of water is required (+) - Very lumpy (+) - Little sticky (+)

- Very difficult (- -) - Easy to get the OMC (+) - A lot of water is required (+ +) - Very lumpy (+ +) - Hard to crush (+ +) - Very sticky (+ +)

M O U L D I N G

- Very difficult (- -) - Less soil is required in the mould (- -) - Very good result with  the penetrometre (+ +)

- Difficult (-) - Less soil is required in  the mould (-) - Not very good result with the penetrometre (-)

- Easy (+) - A lot of soil is required in the mould (+) - Not good result with the penetrometre (- -)

- Very easy (+ +) - A lot of soil is required in the mould (+ +) - Not very good result with the penetrometre (-)

E J E C T I O N

- Very easy (+ +) - Not sticking (-)

- Easy (+) - Not sticking (-)

- Difficult (-) - Very difficult (- -) - Sticks a lot in the corners (+) - High adhesion (+ +) - Sticky in the corners and on the plates (+ +)

H A N D L I N G

- Difficult (- -) - Edges are very fragile (+ +)

- Difficult (- -) - Edges are very fragile (+ +)

- Easy (+) - Edges are fragile (+)

- Very easy (+ +) - Edges are very cohesive (+ +)

H U M I D

A - Very rough surface (+ +) - Not homogeneous (- -) S - “Honey comb” structure P E C T

- Rough surface (+) - Homogeneous (+) - Porous structure

- Smooth surface (+) - Homogeneous (+ +) - Matt finish

- Very smooth surface (+ +) - Very homogeneous (+ +) - Shiny finish

D R Y

A - Easy to break (+ +) - Crumbly (+ +) S - No cracks (-) P E C T

- Easy to break (+) - Crumbly (+) - No cracks (-)

- Easy to break (+ +) - Crumbly (+) - Little cracks (-)

- Very hard to break (+ +) - Very cohesive (+ +) - Big cracks (+ +)

18

PART THREE

COMPRESSED STABILISED EARTH BLOCKS (CSEB)

19

3.1 BASIC DATA ON CSEB (For 5 % cement stabilised blocks) Dry compressive strength σc (After 28 days curing) : 3 to 6 MPa Wet compressive strength σc (After 28 days curing) : 1.5 to 3 MPa (Test done after 3 days immersion)

: 0.5 to 1 MPa

Dry bending strength σb (After 28 days curing) Dry shear strength (After 28 days curing) Water absorption by weight (After 28 days curing) Apparent bulk density (dry) Energy consumption

: 0.4 to 0.6 MPa : 8 to 12 % (Test done after 3 days immersion) : 1700 to 2000 kg/m3 : 110 MJ / m2 Compare this value with Kiln Fired Bricks, Country Fired Bricks and Plain Concrete Blocks (See below) : 16 Kg / m2 Pollution emission (CO 2) Compare this value with Kiln Fired Bricks, Country Fired Bricks and Plain Concrete Blocks (See below) Notes:

- 1 MPa = ± 10 kg/cm 2 - Kiln Fired Bricks are also called Kiln Burnt Bricks or Wire Cut Bricks - CSEB consume per m2, 5 or 15 times less energy than fired bricks and 2.1 times less energy than plain concrete blocks. - CSEB pollute per m2, 2.4 or 7.8 times less than fired bricks and 1.6 times less than concrete blocks.

3.2 SUSTAINABILITY AND ENVIRONMENTAL FRIENDLINESS ¾Earth is a local material. ¾Earth construction is a labour-intensive technology and is an adap table and transferable technology. ¾It is a cost and energy effective material. ¾It is much less energy consuming than fired bricks (5 or 15 times less). ¾It is much less polluting than fired bricks (2.4 or 7.8 times less). 2 ¾A study from Development Alternatives (New Delhi - 1998) gives per m of finished wall: ENERGY CONSUMPTION

POLLUTION EMISSION (CO2)

2

CSEB wall = 110 MJ / m CSEB wall = 16 Kg / m 2 Kiln Fired Brick (KFB) = 539 MJ / m2 Kiln Fired Brick (KFB) = 39 Kg / m2 Country Fired Brick (CFB) = 1657 MJ / m2 Country Fired Brick (CFB) = 126 Kg / m2 Plain Concrete Blocks (PCB) = 235 MJ / m2 Plain Concrete Blocks (PCB) = 26 Kg / m2 Note: Kiln fired bricks are often called wire cut bricks. ¾Be

aware of the management of resources:

It is a crucial issue! If well managed, the production of CSEB will allow new and harmonious developments. On the other hand, if there is no comprehensive management, it can lead to ecological disasters! Always respect our Mother Earth!

3.3 HOLLOW INTERLOCKING BLOCKS FOR EARTHQUAKE RESISTANCE A technology using reinforced hollow concrete block has been developed all over the world since a while. Its principle is to reinforce the masonry by grouting a concrete into the holes of the blocks where stands a steel rod at the critical locations (Corners, ends, near openings, etc,). Horizontal reinforcements are also cast in blocks with a U shape. The technology using Hollow Interlocking Compressed Stabilised Earth Blocks (HI CSEB) is based on the same principle: to reinforce horizontally and vertically the masonry with Reinforced Cement Concrete (RCC) members. The advantage of hollow interlocking CSEB, compared to hollow concrete blocks, is that they offer keys, which interlock in the other blocks. Thus these walls offer more resistance to shear and buildings would be even stronger. They would better resist earthquakes and without major damages. Compressed stabilised earth blocks have another advantage: they are in most cases cheaper and they are always more eco-friendly than concrete blocks. 20

¾Particular requirements for hollow

interlocking blocks

Interlocking blocks can resist disasters (Cyclones, earthquakes and floods), provided that they are hollow, so as to be reinforced with Reinforced Cement Concrete (RCC), at regular intervals. A hollow interlocking CSEB for earthquake resistance must satisfy these requirements: - Extreme consistency in height (1 mm difference maximum is allowed). - Self-aligning to reduce time-wasting adjustments. - Blocks should be hollow and the vertical holes and U shaped blocks should allow casting RCC, according to requirements: To reinforce regularly the masonry vertically and horizontally. - The interlocking keys must interlock transversally and longitudinally to the wall. They should interlock  especially well in the length of the wall, which is subject to the shear stress of the earthquake. - Every course must interlock with each other as well as the header of every block in length: to increase  the shear strength of the masonry. - Good seating of the blocks on top of each other for properly transmitting the load bearing: All the block  area, including the key, must transmit the load. - A binder must bind them: they must not be dry stacked, as the aim is to get a homogenous masonry. - The binder should be a cement-sand mortar of 5 mm thick. It should be quite fluid in order to be workable. - The mould must allow manufacturing of full size blocks but also 3/4 and 1/2 sizes. The blocks must not be cut to match the bond pattern, which will be detrimental to the accuracy, strength and quality of the masonry. Compressed stabilised earth blocks have a poor bending strength (See table page 20) but this is not so critical because the block itself will not bend but the masonry will do. CSEB have very poor shear strength, which is critical in the case of earthquakes. Interlocking blocks will not have a stronger shear strength compared to ordinary CSEB. But the key effect will increase the shear strength of the masonry if the cohesiveness of the material is high enough to keep the link between the key and the body of the block. (Especially shocks and vibrations of an earthquake) ¾The Auram hollow interlocking blocks

The accuracy of the Auram press allows a very regular block height: only 0.5 mm difference in height. This allows the block to get the ideal mortar thickness of 5 mm. Therefore, the block modules are: - 30 x 15 x 10 cm for the rectangular block 295 (29.5 x 14.5 x 9.5 cm). - 25 x 25 x 10 cm for the square block 245 (24.5 x 24.5 x 9.5 cm). The hollow interlocking 295 is only meant for single storey buildings. The hollow interlocking block 245 can safely be used up to two storey buildings only. The holes have been maximized (regarding the size of the block and the press design) at 5 cm diameter to allow a proper concrete cover for the steel. The area of the key has been maximized at 9 cm diameter to ensure the maximum adhesiveness of the key on to the block body, so as to resist the shear effect. The height of the key has been determined by having  the maximum friction area between blocks to resist the shear and by having the minimum friction on the mould while de-moulding the block from the press. The chamfer angle of the key seeks to be optimum.

Variety of blocks 295

Variety of blocks 245 21

3.4 BLOCKYARD ORGANIZATION ¾6

Stages

2 to 4 persons 1 person 2 persons 3 persons 1 person 2 persons

- Preparation (Digging + Sieving) - Measuring - Mixing (dry + wet) - Pressing - Initial curing and first stacking - Final curing and stacking

transport ⇒ transport ⇒ transport ⇒ transport ⇒ transport ⇒ transport ⇒

11 to 13 persons Note: - These numbers are valid for one AURAM press 3000, which can produce 1000 blocks 240 per day,

600 blocks 245 or 295 per day. - The number of persons for the digging & sieving will vary with the type of soil. - The number of persons for the final curing & stacking will depend of the transportation distance. ¾Quality control

Do it at every stage of the production line. ¾Key

words

- Reduce the distance of transportation. - Optimise the ratio output / number of workers, to get the best efficiency. - Organize the block-yard as close as possible from the site. - It is preferable to have a linear organization but a circular one can also be suitable. ¾Typical linear organization

3.5 QUALITY CONTROL ¾Golden rules

- To create a joyful atmosphere where every body is conscious of the quality required and check the blocks. - Check the production at every stage (see the production cycle). - Check the quality of the compression with the pocket penetrometre, always for the first block of every mix. - Check the height with the block height gauge, always for the first block of every mix. - Follow daily the production. Record the output, the dates... - Check weekly or monthly, the production with the field block tester (after 28 days).

22

¾During the production

STAGE

WHAT TO CONTROL • •

Soil supply

• • • • •

Sieving

• • •

Measuring • • •

Dry mixing • • •

Wet mix • • • •

Pressing

• •

•

Initial curing And First stacking

• • • • • •

Final curing And Stacking

• • • •

MEANS

The topsoil must be removed. Check the regularity of the supply. Check the depth of veins. If the supply is with lorries, check before unloading. Check the root contents. Adapt the mix if there are some changes in soil supply.

•

Sensitive analysis.

Angle of the sieve. Size of the lumps. Percentage of waste.

•

Look.

Check that containers are filled according to the requirements. Check that 1 bag of cement is poured in buckets at once.

•

Look.

Move 2 times minimum the piles (the best is 3 times). Check the uniformity and homogeneity of the mix. (Especially the colour) Check if there are big lumps and crush them.

•

Look.

Move 2 times minimum the piles (the best is 3 times). Check the uniformity and homogeneity of the mix. (Especially the colour) Check the lumps and crush them, if any. Check the moisture content.

•

Look. Sensitive analysis

Check the strength with the pocket penetrometre. Check the height with the block height gauge. See the texture (loose or dense). Have an external look. (Edges, corners, difference in colours, etc.)

•

•

Block height gauge. Penetrometre Look.

If the stacking is according to requirement. If the ground is cleaned regularly. The blocks are properly covered with plastic sheets. The quality of the edges after stacking. Check the spaces left in between blocks.

•

Look.

•

Look.

Care for the transport. Care for stacking. If the stacking is according to the requirement. Good protection of the piles’ top with coconut leaves straw or any material for the sunshade. Water during 4 weeks, minimum twice daily (according to  the weather). The blocks must not dry during 4 weeks! Drying for 4 weeks before use. 23

•

•

¾After the production

- Record the data

- Number of workers & number of hours worked - Number of bags and number of blocks produced - Calculate the Number of blocks per mix and per bag of cement (not more than ± 2 blocks difference according to average production). - Obviously an entrepreneur will need also to record his stock, salaries, and so on, to manage properly his unit. - Field bending test = Bending test σb = 3 x F x L

2 x W x H2 F L W H

= load applied on the block, in kg. = distance of the supports, in cm = Width of the block, in cm = height of the block, in cm

σc = ± 5 σb

(This coefficient 5 varies from soil to soil) - Laboratory tests

Bending + compression + shear crushing + water absorption. ¾Practical

grid for the bending strength test

When testing the blocks by bending, not a single block should break below the following load (loa d applied on the plate). Then, they will resist to a minimum of 5 kg/cm2 of bending strength, which is within the limits of 5 to 10 kg/cm2 by dry bending crushing strength. Height

Block 290 (29 x 14 cm)

Block 240 - 4/4 (24 x 24 cm)

Block 240 –1/2 (24 x 11.5 cm)

(cm) 10 9 8 7 6 5

Load on the plate (kg) 50 40 30 20 12.5 7.5

Load on the plate (kg) 85 70 52.5 37.5 27.5 17.5

Load the on plate (kg) 40 35 22.5 15 10 5

Note: - The load is the weight applied on the plate of the field block tester.

- The weight of the plate from the Auram field block tester is 6.5 kg. - The space between the angle of the field block tester is L = 18 cm. - The calculation takes in account the leverage (5 times) of the AURAM field block tester.

24

3.6 COST ANALYSIS ¾Hollow

interlocking block 245 produced on site

Block size: 24.5 x 24.5 x 9.5 cm, with 5% cement

Value: Auroville, April 2005, 1 US $ = ±43.5 Rs.

 MAIN DATA

Press lifespan (600 strokes per day over ± 5.5 years = 10 Lakhs of blocks) (Blocks) Daily production (Blocks) Annual production = Daily prod. x 26 days x 11 months (1 month = maintenance +heaviest rains) Equipment cost (Rs.) 2 2 Buildings [storeroom 15 m , simple production shed 75 m ] and infrastructure (Rs.) Maintenance for the lifespan of the press (Rs.) VARIABLE COSTS

Labour (Man) Soil (± 80 % = 7.69 m 3 per 1000 blocks) Sand (± 20 % = 1.92 m3 per 1000 blocks) Cement (5 % = 12.82 bags per 1000 blocks) Maintenance per block

Rs./Unit

Units

Cost / Block

%

100 70 360 150 0.025

8 4.58 1.14 7.63 1.00

1.333 0.534 0.684 1.907 0.025

26.70 % 10.69 % 13.70 % 38.18 % 0.50 % 89.76 %

TOTAL Variable costs (Rs.)

 FIXED COSTS

Investment Cost (Interest) Equipment Depreciation (= press lifespan) Building Depreciation (= site duration) Overheads / Miscellaneous

1,000,000 600 171,600 125,000 40,000 25,000

4.483 %

Total Rs.

5.0 % 16.8 % 50.0 % 5.0 %

165,000 125,000 40,000 4.483

Cost / Block

0.048 0.122 0.117 0.224

TOTAL Fixed costs (Rs.)

0.511

TOTAL cost per block (Rs.)

4.99

%

0.96 % 2.45 % 2.33 % 4.49 % 10.24% 100.00 %

NOTES

- The production is done on a construction site, which has the minimum set up (simple storeroom, light production shed). The latter would be wasted at the end of the site. - The equipment includes 1 Auram press 3000 + 1 mould, 1 wheelbarrow 200 Litres, 1 wheelbarrow 350 Kg, 1 soil sieve # 10 mm, 1 sand sieve # 4 mm, plastic sheets, barrel and small tools. - The soil is extracted from the site and its cost includes sieving in the quarry. - The sand cost includes delivery by lorry and sieving on site. - The water cost is included in the overheads / miscellaneous. - The labour cost includes the yearly bonus and the Employee Providence Fund. ¾Comments

- The depreciation cost of the equipment, the maintenance of the equipment and the investment cost is only 3.41 % when the cement is 38.18 % and the labour 37.39 % (for block-making and soil digging). This implies that one should find a way to reduce the cost of the stabiliser but not the manpower with unskilled labour or the equipment with cheap presses. - The soil dug on site, costs 70 Rs./m3 that mean 0.534 Rs./block. If it has to be delivered by lorry, its cost per block would become Rs. 1.152. Thus the cost price of the block would be Rs. 5.64 instead of 4.99. - If the blockyard is organised with a moveable shed, the cost price of a block will be slightly cheaper than for   the site production (Rs. 4.91) because the building depreciation is less than for the site production. ¾Cost

comparison with Country Fired Bricks (CFB)

This comparison includes the difference for the volume & breakage: - Plain CSEB 240 = 24 x 24 x 9 cm with 5% waste at a cost of 4.47 Rs./Block comes to 4.69 Rs. /Block. - Hollow interlocking CSEB=24.5 x 24.5 x 9.5cm+5% waste at a cost of 4.99 Rs./Block comes to 5.24 Rs./Block. - Country fired brick = 22.0 x 10.5 x 6.5 cm with 12% waste at a cost of 1.425 Rs./Brick comes to 1.60 Rs. /Brick. - As CSEB and CFB have a different size, the cost by volume (including the wastage) is now: Plain CSEB 240 = 906 Rs./m3 Therefore, per m3 of raw material, CSEB 240 is 17.3 % cheaper Hollow CSEB 245 = 920 Rs./m3 than CFB, and HI CSEB 245 is 15.5 % cheaper than CFB. But Country fired brick (CFB) = 1063 Rs./m3 the cost per m3 of masonry is quite different (see next page) 25

¾Cost

analysis of CSEB masonry with hollow interlocking blocks, produced on site DATA

Item

HI CSEB 245 (24.5 cm thick) Rs.

Blocks 245 + 5% waste Block 295 + 5% waste Mortar CSM 1: 4 PCC 1: 1.5: 3 Chips (m3) PCC 1: 1.5: 3 Gravel(m3) Steel Φ10TS, Φ6MS (Kg) 1 Mason 2 Helpers 1/2 Labour male 1/2 Labour female

Data

5.24 4.25 1619 1769 1726 25.0 150 75 100 60

HI CSEB 295 (14.5 cm thick) Rs. Data

2

40 Full blocks per m x 1.05 2

17.0 Litres per m of wall 15.6 Litres/m2 for all the holes 10.8 Litres/m of ring beam 1.4 Kg per m2 of wall 4 m2 of wall laid per day 4 m2 of wall laid per day 4 m2 of wall laid per day 4 m2 of wall laid per day

220.2

5%

28.9 27.5 18.7 35.0 37.5 37.5 12.5 7.5 425.4 21.3

TOTAL PER M2

447

SUB TOTAL PER M2

Miscellaneous

Rs.

33.33 Full blocks per m2 x 1.05 9.5 Litres per m2 of wall 12.8 Litres/m2 for all the holes 5.2 Litres/m of ring beam 1.3 Kg per m2 of wall 5.4 m2 of wall laid per day 5.4 m2 of wall laid per day 5.4 m2 of wall laid per day 5.4 m2 of wall laid per day

148.9 16.1 22.6 9.0 32.3 27.8 27.8 9.3 5.6 299.3 15.0 314

3

TOTAL PER M 1,823 2,167 Reinforcement detail ( 10 TS): 1 vertical tie per running metre + 2 bars per ring beam + PCC in all the holes and 1 ring beam ¾Cost comparison of masonry

- Data (Materials delivered on site)

- Mason = 150 Rs./day – Helper = 75 Rs./day – Labour male = 100 Rs./day – Labour female = 60 Rs./day - KCP 43 grades = 150 Rs./bag – Sieved soil = 70 Rs./m3 – Sieved sand = 360 Rs./m3 - Plain CSEB 240 = Rs. 4.47 – Hollow Interlocking CSEB 245 = Rs. 4.99 - CFB = Rs. 1.425 – WCB = Rs. 3.50 (WCB are Wire Cut Bricks, also called kiln-fired bricks) - Cost price of walls:

- CSEB wall 24 cm thick (Block 240 without plaster) - HI CSEB wall 24.5 cm thick (Block 245 without plaster) - CFB wall 21.5 cm thick (without plaster) - WCB wall 23 cm thick (without plaster) ⇒ ⇒

= 320 Rs./ m 2 = 447 Rs./ m2 = 398 Rs./ m2 = 599 Rs./ m2

= 1334 Rs./m3 = 1823 Rs./m3 = 1810 Rs./m3 = 2724 Rs./m3

Per m3 of finished wall, CSEB 240 are 26.3 % cheaper than CFB and 51.0 % cheaper than WCB. Per m3 of finished wall, HI CSEB 245, with reinforcements, are 36.6 % costlier than CSEB 240, and nearly the same cost as CFB (0.7 % costlier) and 33.0 % cheaper than WCB.

3.7 ECONOMIC FEASIBILITY STUDY

Today, many small entrepreneurs would like to manufacture blocks to sell them. Indeed, it can be an interesting business, if it is well managed and properly organized. This study is done for Auroville context in March 2005, for the hollow block 245 (24.5 x 24.5 x 9.5 cm). The example studied is for village scale production with manual equipment for 2000 Blocks output per day (2 Auram presses 3000). It shows that  the project starts to be viable when two machines are working. The reason is that the fixed costs (overheads: manager, storekeeping. Etc.) are nearly the same if the unit has one or several presses. ¾Notes for the feasibility study

- Equipment includes: 2 Auram press 3000 + mould 245, 2 wheelbarrow 200 Litres, 2 wheelbarrow 350 Kg, 2 soil sieve #10 mm, 2 sand sieve # 4 mm, plastic sheets, 2 barrels and small tools. - Buildings are moveable: office 10m2, storeroom 20m2 and a production shed 75 m2. They are re-used later on. - The management and labour cost includes the yearly bonus and the E mployee Providence Fund. - The yearly production is only on 11 months (For maintenance of equipment and heaviest rains) - The loan for the working capital is a demand loan (Short term): Thus, it is not shown in the Inflow / outflow. - The sand cost includes delivery by lorry and sieving on site. - The soil cost includes digging and sieving on site. - Value: Auroville, April 2005, 1 US $ = ±43.5 Rs 26

ECONOMIC FEASIBILITY – HOLLOW 245 (245 x 245 x 95 mm - 5 % cement) – ON-SITE PRODUCTION  MAIN DATA Daily production per press Number of presses Months worked yearly Days worked yearly @ 26 days per month  Yearly production Maintenance per press (Lifespan) Production cost per hollow block 245 Profit margin Inflation rate

600 1 11 286 171,600 25,000 4.99 24 % 4%

Blocks No. Months Days Blocks Rs. Rs.

 PROFIT AND LOSS ACCOUNT (INCOMES & EXPENDITURES)  Incomes Cost / Unit Units Year 1 1,062,661 Sales of blocks (All blocks made are sold) Other Income (Profit or loss on sales of assets)  Direct costs (Variable costs) Labour per day (Man) 100 8 249,600 Soil per day (± 80 % = 7.63 m 3 per 1000 blocks) 70 4.58 91,652 3 Sand per day (± 20 % = 1.90 m per 1000 blocks) 360 1.14 117,374 Water per month: it is paid by the site (Months) 0 11 Cement per day (5 % = 12.71 Bags per 1000 blocks) 150 7.63 327,155 Repair and Maintenance (Number of Presses) 25,000 1 7,143 Total Direct costs 792,924 Overhead costs (Fixed costs) Manager and supervision (Months) 6,600 12 79,200 Watchman and premises maintenance (Months) 1,300 12 15,600 Interest (On capital investment & working capital) 19,017 Equipment depreciation 16.8 % 125,000 21,000 Buildings & Infrastructure depreciation 50 % 40,000 6,667 Total Overhead costs 141,483 NET PROFIT before tax

 PROJECT CASH FLOWS Cost / Unit Units

YEARLY OUTFLOWS (EXPENDITURES) Capital investment  Equipment Buildings & Infrastructure Total Capital investment  Variable costs (Same as Profit & Loss Account)  Fixed costs (Overhead costs) Manager and supervision (Months) Watchman and premises maintenance (Months) Interest on Capital Investment Interest on Working Capital Repayment of Loan (Years) Total Fixed costs TOTAL YEARLY OUTFLOWS YEARLY INFLOWS (INCOMES) Sales of Blocks (All blocks made are sold) Equity participation (Owner's share) Loan for capital Investment (Bank's share) Sale of moveable assets (Equipment only) TOTAL YEARLY INFLOWS

Year 2

Year 3

1,105,168

1,149,374 - 137,750

259,584 95,318 122,069 340,242 7,429

269,967 99,130 126,952 353,851 7,726

824,641

857,627

82,368 16,224 16,820 21,000 6,667

85,663 16,873 14,642 21,000 6,667

143,079

144,844

128,254

137,447

13,153

Year 1

Year 2

Year 3

792,924

824,641

857,627

79,200 15,600 7,920 11,097 22,000

82,368 16,224 5,280 11,540 22,000

85,663 16,873 2,640 12,002 22,000

135,817

137,412

139,178

1,093,741

962,054

996,805

1,062,661 99,000 66,000

1,105,168

1,149,374

125,000 40,000 165,000

6,000 1,300 66,000 73,977 66,000

6.19 60 % 40 % 25 %

12 12 12 % 15 % 3

171,600 165,000 165,000 1250,000

31,250 1,227,661

NET CASH FLOW 

133,921

27

1,105,168

1,180,624

143,11 183,820

ECONOMIC FEASIBILITY – HOLLOW 245 (245 x 245 x 95 mm - 5 % cement) – BLOCKYARD PRODUCTION  MAIN DATA Daily production per press Number of presses Months worked yearly Days worked yearly @ 26 days per month  Yearly production Maintenance per press (Lifespan) Production cost per hollow block 245 Profit margin Inflation rate

600 2 11 286 343,200 25,000 4.91 35 % 4%

Blocks No. Months Days Blocks Rs. Rs.

 PROFIT AND LOSS ACCOUNT (INCOMES & EXPENDITURES)  Incomes Cost / Unit Units Year 1 2,276,059 Sales of blocks (All blocks made are sold) Other Income (Profit or loss on sales of assets)  Direct costs (Variable costs) Labour per day (Man) 100 16 499,200 Soil per day (± 80 % = 7.63 m 3 per 1000 blocks) 70 9.16 183,303 Sand per day (± 20 % = 1.90 m3 per 1000 blocks) 360 2.28 234,749 Water per month: Electricity cost for the pump (Months) 250 11 2,750 Cement per day (5 % = 12.71 Bags per 1000 blocks) 145 15.25 654,311 Repair and Maintenance (Number of Presses) 25,000 2 14,286 Total Direct costs 1,588,598 Overhead costs (Fixed costs) Manager (Also for accounting and marketing) 6,600 12 79,200 Premises maintenance (Cleaning the premises) 1,300 12 15,600 Supervisor (Also for storekeeping and maintenance) 4,000 12 48,000 Miscellaneous (Office expenditure) 4,000 12 48,000 Interest (On capital investment & working capital) 76,338 Equipment depreciation 16.8 % 250,000 42,200 Buildings & Infrastructure depreciation 5% 128,000 6,400 Total Overhead costs 315,538 NET PROFIT before tax

 PROJECT CASH FLOWS Cost / Unit Units

YEARLY OUTFLOWS (EXPENDITURES) Capital investment  Equipment Buildings & Infrastructure Water (Well, Pump and Tank) Land: blockyard & excavation for the exercise (Acre) Total Capital investment  Variable costs (Same as Profit & Loss Account)  Fixed costs (Overhead costs) Management Interest on Capital Investment Interest on Working Capital Repayment of Loan (Years) Total Fixed costs TOTAL YEARLY OUTFLOWS YEARLY INFLOWS (INCOMES) Sales of Blocks (All blocks made are sold) Equity participation (Owner's share) Loan for capital Investment (Bank's share) Sale of moveable assets (Equipment only) Sale of land with the water supply (Immoveable assets) TOTAL YEARLY INFLOWS

300,000

2.08

Year 2

Year 3

2,367,102

2,461,786 - 315,500

519,168 190,635 244,139 2,860 680,483 14,857

539,935 198,261 253,904 2,974 707,703 15,451

1,652,142

1,718,228

82,368 16,224 49,920 49,920 59,196 42,000 6,400

85,663 16,873 51,917 51,917 42,089 42,000 6,400

306,028

296,859

371,922

408,931

131,199

Year 1

Year 2

Year 3

1,588,598

1,652,142

1,718,228

190,800 54,096 22,242 150,267

198,432 36,064 23,132 150,267

206,369 18,032 24,057 150,267

250,000 128,000 125,000 624,000 1,127,000

15,900 450,800 148,283 450,800

6.63 60 % 40 % 25 % 100 %

NET CASH FLOW 

28

12 12 % 15 % 3

343,200 1,127,000 1,127,000 250,000 749,000

417,405

407,895

398,725

3,133,004

2,060,037

2,116,953

2,276,059 676,200 450,800

2,367,102

2,461,786

62,500 3,273,286 3,403,059

2,367,102

3,273,286

270,056

307,064

1,156,332

PART FOUR

DESIGN AND MASONRY

29

4.1 BASIC DESIGN GUIDELINES FOR CSEB ¾General

principles for a good design

- “Good boots and a good hat”.

That means built a good basement: (Minimum 25-cm high) And good overhangs: (Minimum 25 cm wide or better 50 cm)

¾Compressive strength for earthquake resistant CSEB

- Design the walls (thickness + stability) according to the load bearing capacity of wet CSEB. - The minimum admissible crushing load of HI CSEB should be 25 Kg/cm2 under wet conditions.

(After 3 days immersion) - Keep at least a safety factor of 10 from the wet crushing strength (σc) for HI CSEB. Example: A HI CSEB has a σc wet of 25/kg/cm2: the maximum load bearing for the basement will be: 25 = 2.5kg/cm2 10 ¾Shear strength

- Avoid any major difference of load bearing in CSEB walls:

especially with a different floor height.

¾Water absorption and erosion.

- Avoid any concentration or accumulation of water in any part or surrounding of the building. - Avoid any run off of water on any part of the building (i.e. leakage) ¾Module of blocks

- Design the building according to the module of blocks.

The module of the block is its nominal size + the mortar thickness.

30

¾How

to dimension a building

A strong and clean block-work must follow the block module. The dimension of the building should fit with  the block module theory: A B C

= Outside to Outside = Inside to Inside = Outside to Inside

= (X . M) - J = (X . module) – 0.5 cm = (X . M) + J = (X . module) + 0.5 cm = (X . M) = (X . module)

M= module of the block = the block dimensions + the mortar joint thickness. J = joint thickness The module for the Auram block 245 is 25 cm and the joint thickness is 5 mm, which is the optimum joint  thickness for interlocking blocks.

31

4.2 BASIC DESIGN GUIDELINES FOR EARTHQUAKE RESISTANCE ¾Building

shapes

The best shapes for earthquake resistant buildings are regular shapes and preferably with two symmetry axes. In this case the centres of gravity and rigidity will be the same or close to each other and therefore  there will not be any torsion in the building. Round buildings behaved particularly well during the 2001 earthquake of Gujarat, especially those that were built in adobe bricks. When it is not possible to have regular shapes, it is possible to improve the earthquake resistance by dividing the building in several parts.

GOOD SHAPES

DEFFICIENT SHAPES AND IMPROVEMENT ¾Separation

gap

Buildings with irregular and asymmetrical shapes are more fragile than simple ones. Hence they should be split into simpler shapes like shown above. These various parts will vibrate at a different frequency and amplitude under the reversible ground shakings. Therefore they will hit each other and will be mutually damaged. A gap should be kept between them to avoid collision. This gap can be filled with a crumbly material, which will be crushed under the shocks, or it can be left empty. In both cases, care should be taken for the waterproofing of the joint with a system that does not link  again both parts. The separation gap must be minimum 25 mm for ground floor buildings and for higher ones the gap should be increased by 10 mm per storey more. (Ref. IS 4326: 1993) ¾Ductility

Masonry components are most of the time brittle ones. Some reinforcements can be added to make a structure more ductile with these brittle materials. Wood and bamboo can be advantageously used. Reinforced cement concrete members are always more efficient, when they are well done and well distributed. Ring beams at various levels, which are linked together with vertical ties, will reinforce the structure very well and make it ductile. 32

¾Rigidity distribution

The centre of gravity of the plan should also preferably be the centre of rigidity of the vertical masses. This would avoid torsion of the building.

PROPER DISTRIBUTION OF WALLS AND OPENINGS

WRONG SHAPE

BAD DISTRIBUTION OF WALLS / O PENINGS

TORSION DUE TO BAD DESIGN

The vertical rigidity of the building should also be well distributed. Change in the structural system from one floor to another or different building height would increase the damage potential. Vertical ties should link the various floors and ring beams.

¾Simplicity

Simplicity in the ornamentation is the best approach. Large cornices, vertical or horizontal cantilevered projections, cladding materials, etc. are dangerous during earthquakes. They should be avoided. ¾Foundations

Certain types of foundations are more susceptible to damage than others. Isolated footing of columns can easily be subjected to differential settlement, particularly when they rest on soft soils. Mixed foundations in  the same building are also not suitable. What works best in most of cases are trench foundations.

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¾Long

walls

They should be designed as shear walls to resist the ground motion in the plane of the wall. To resist the bending moment occurred by the ground motion perpendicular to the wall, they should be braced either by a buttress or by a cross wall. Any opening in a wall should follow the specifications mentioned in the next paragraph.

CROSS WALL NEAR THE CENTRE

BUTTRESS IN THE CENTRE ¾Openings

Doors and windows reduce the lateral resistance of walls to shear. Hence, they should preferably be small and rather centrally located. When a specific design cannot follow this basic specification, the specifications mentioned below (IS 4326: 1993) must be followed.

D1, D2 = Doors

W1, W2, W3 = Windows V1, V2 = Ventilators CW = Cross walls T = Thickness of cross walls B8 is wider than B2 - B7 is wider than B9 1 STOREY

B1 +B2 + B3 B6 +B7 B4 B5 H3 H4

0.5 L1 ≤ 0.5 L2 ≤

2 STOREY

3 STOREY

0.42 L1 ≤ 0.33 L1 ≤ 0.42 L2 ≤ 0.33 L2 0.5 H2 (But not less than 60 cm) 0.25 H1 (But not less than 60 cm) 0.5 B8 (But not less than 60 cm) 0.5 B7 (But not less than 60 cm) ≤

Notes:

- H3 is calculated from B8, which is wider than B 2 - H4 is calculated from B7, which is wider than B 9

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4.3 DESIGN GUIDELINES FOR HOLLOW INTERLOCKING BLOCKS

Hollow interlocking compressed stabilised earth blocks must be bound by cement sand mortar, in order to get a homogeneous and cohesive masonry. The blocks should not be dry stacked. The design for these blocks should follow the basic design guidelines mentioned in the two precedent paragraphs. The following specifications should be added to increase the masonry strength. ¾Trench Foundations

Any appropriate material can be used for the foundations. Stabilised rammed earth will be a very appropriate solution if the natural ground is suitable. Stabilised rammed earth foundations normally have a square section: i.e. 60 x 60 cm for a ground floor structure. Note that isolated foundations, like footings of columns, are not adapted. On coastal areas, which are tsunami prone, buildings should have deeper foundations. Its minimum depth should be double the width: i.e. 60 cm wide x 120 cm deep. This will avoid the bearing ground of the foundations to be excavated by the flow. If Reinforced Cement Concrete (RCC) foundations are to be used it is essential that the vertical ties are inserted very accurately from the bottom of the foundation. ¾Basement

It can be done with various materials, by steps or like a monolithic plinth. Note that the height of the basement varies with local conditions. The example shown below is the minimum height. A RCC ring beam is embedded at the top of the foundation and a plinth beam at the floor level should always be cast: - At the top of the foundation (unless RCC foundations are used) is laid a first a reinforced concrete ring beam, 1cement: 1.5sand: 3gravel, in which are anchored the vertical ties. - It is essential top locate very accurately the vertical ties in the first reinforced concrete ring beam. - Above it starts the step plinth and its height depends of the local conditions. The minimum height will be  two blocks above the first concrete ring beam, as shown below. - A plinth beam is laid on the basement and its top level will be the floor level. This plinth beam is cast in U blocks with 1cement: 1.5sand: 3gravel. All courses of the step basement are laid in stabilised earth mortar, SEM: 1cement: 1 soil: 3 sand. The mortar thickness is everywhere 5 mm thick, for the horizontal and vertical joints. Note that on top of the plinth beam will be laid a damp-proof course of 1 cm thick with CS 1: 2 and waterproofing compound.

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¾Ring

beams

They tie horizontally the building and the maximum vertical spacing between them should be 120 cm and  the minimum should be 50 cm (below the roof). They are 5 or 6 ring beams, depending on the case: - Roof with a concrete slab or ferrocement channels = 5 ring beams. - Roof with a vault or dome and a parapet wall = 6 ring beams. If windows have arches and not lintels, the lintel ring beam should be on top of the arch. Reinforcements are made with 2 bars of Ø10TS and stirrups Ø6MS @ 25 cm c/c maximum.

Ring beams for ferrocement channels

Ring beams for RCC slab roof

Ring beams for vaulted roof

Reinforcement bars are made with Tor steel bars of Ø 10mm. It is preferable to prepare long reinforcements and to join them in the corners with angle bars. These angles bars are also made with Ø10mm Tor Steel (TS) rods and their side length should be 50 times the diameter of the bar (50cm side):

¾Vertical ties

The ring beams are tied together with vertical ties (Ø 10 TS), so as to create reinforcement net. The vertical ties are laid on the foundation and anchored in a PCC 1: 1.5: 3, just above the foundations. The bars should be bend 30 cm in the PCC and their height will not exceed 150 cm, so as to slide down the blocks. The overlap of the extension rod will be 50 times the bar diameter (50 cm for Ø 10TS). They should follow the spacing shown hereafter. BLOCK 245

BLOCK 295

¾Long

walls ¾Openings

Maximum every 200 cm 1 bar, on either side, in the first hole, (At 12.5 cm) ¾L Corner walls 1 bar on either side, in the first hole from  the inside corner (At 12.5 cm) and 1 bar  centred in the L bar on 3 sides, in the first hole from the ¾T Cross walls inside corner (At 12.5 cm) and 1 bar  centred in the T bar on 4 sides, in the first hole from the ¾ X Cross walls inside corner (At 12.5 cm) and 1 bar  centred in the X  36

Maximum every 150 cm 1 bar on either side, in the first hole, (At 15cm) 1 bar on either side, in the first hole from the inside corner (At 15 cm) 1 bar on 3 sides, in the first hole from  the inside corner (2 bars at 30 cm, on  the length and 1 bar at 15cm on the T) 1 bar on 4 sides, in the first hole from  the inside corner (At 30 cm)

Location of vertical ties ¾Large opening

In case of a large opening in a facade (i.e. veranda), it must have a shear wall at least on one side, or several smaller  shear walls. The total length of these small shear walls will not be less than the half of the front facade. This (these) shear wall(s) will be more reinforced: Vertical ties (∅ 10 TS) will be placed in the first hole close  to the end or corner and at maximum spacing between them of 60 cm (block 295) or 75 cm (block 245). In the case of a veranda, the sidewall will be reinforced with a buttress, not less than 30 cm, from the inside corner. ¾Binders

- Stabilised Earth Mortar SEM 1: 1: 3

All courses should be bound by cement stabilised earth mortar 1 cement: 1 soil: 3 sand. It should be plastic and not too liquid. The soil should not have more than 20-25 % of clay. All joints, horizontally and vertically, are 5 mm thick. Note a cement sand mortar (i.e. 1: 4) will have a very low workability as the mortar thickness is only 5mm. Note for all courses: The blocks must be soaked before being laid and a well-laid block is impossible to remove with one hand because it sticks well to the cement sand mortar. - Plain Cement Concrete 1: 1.5: 3

All the holes, with or without reinforcement, and all ring beams, are filled with plain cement concrete 1: 1.5: 3. The plasticity of the concrete for the holes is rather fluid, but not liquid. It should flow well in  the holes without being a soup. It is essential to compress very well the concrete with a steel rod. 4.4 LAYING HOLLOW INTERLOCKING COMPRESSED EARTH BLOCKS (HI CSEB) ¾ Plinth beam

Execute very well the basement: The plinth must be absolutely levelled and well done. The quality and linearity of the walls with interlocking blocks will depend a lot on the linearity of the plinth. On top of the plinth beam is laid a damp-proof course of 1 cm thick with CS 1: 2 and waterproofing compound. Plinth beam and first course

Steel detail in the corner Insert vertical tie and pipe 37

Lay the first course

Check spacing with a block 

¾

All courses above the plinth beam

1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10

¾

Brush the plinth beam from any dust or sand, and soak it. Start the course above it by applying the mortar in a corner: Apply 7-8 mm thick. Soak a HI CSEB into water and stick it immediately on the mortar. Press it well. Adjust it immediately with a spirit level and a plumb line. Adjust its direction with a straight edge. Check the height with a meter tape to get 5 mm joint. Do the same in the opposite corner and stretch firmly a string line between them with the special device. Do not let wet blocks touch the ground: they should not to catch any d ust or sand. Apply mortar (7-8 mm thick) on the plinth and on the header of the previous block. Soak a HI CSEB into water and stick it immediately on the mortar and against the header of the previous block. Adjust the linearity of the masonry by following the string line and rule (top and side of the wall). Once the first course above the plinth / ring beam is completed, check that the length of the wall is correct. If necessary, adjust the spacing between the blocks, to get a 5 mm joint, and the correct dimension. The walls should be regularly cleaned and every evening, the joints should be pointed with the same mortar 1 cement: 1 soil: 3 sand. Once the mortar for pointing start to set, the masonry will be advantageously cleaned with a humid sponge to remove any stains of cement mortar on the blocks.

Filling the holes with or without reinforcement: PCC 1: 1.5: 3

1. Lay ∅ 10 TS rods for the vertical ties, according to the specifications. Don’t forget to provide an overlap of 40 cm (50 times the TS rod diameter) for every extension of these rods. 2. Cast cement concrete every 2 or 3 courses (1cement: 1.5 sand: 3 gr avel chips ¼”). 3. Use a piece of ∅ 10 TS rod to push PCC down and compressed it well. 4. Lay more blocks of regular courses and then lay a course of U blocks. 5. Lay the horizontal reinforcement ( ∅ 10 TS rods) of the ring beams. Link the vertical reinforcements by bending them in the U blocks (only with the top ring beam). Pour PCC (1 cement: 1.5 sieved sand: 1.5 gravel chips ¼”: 1.5 gravel ½”). ¾

Cure daily the walls

The walls must be cured daily, as many times as required, for 28 days. Do not let it dry during 4 weeks. ¾

Materials requirement per m 2 of wall (including pointing & wastage) BLOCK 295 = 33.33 blocks per m2 BLOCK 245 = 40 blocks per m2 Mortar 1: 1: 3 (1 Cement: 1 Soil: 3 Sand) Mortar 1: 1: 3 (1 Cement: 1 Soil: 3 Sand)

Quantity of cement = 3.4 Litres Quantity of soil # 1mm = 3.4 Litres Quantity of sand # 1mm = 10.2 Litres

Quantity of cement Quantity of soil # 1mm Quantity of sand # 1mm

Concrete 1: 1.5: 3 for all holes

Concrete 1: 1.5: 3 for all holes

(1 Cement: 1.5 Sand: 3 gravel chips ¼“) Quantity of cement = 2.85 Litres Quantity of sand # 5mm = 4.27 Litres Quantity of gravel chips ¼“ = 8.55 Litres

(1 Cement: 1.5 Sand: 3 gravel chips ¼“) Quantity of cement = 3.4 Litres Quantity of sand # 5mm = 5.1 Litres Quantity of gravel chips ¼“ = 10.2 Litres

Concrete 1: 1.5: 1.5: 1.5 for one ring beam

Concrete 1: 1.5: 1.5: 1.5 for one ring beam

(1Cement: 1.5Sand: 1.5gravel ¼“: 1.5gravel ½“) Quantity of cement = 2.4 Litres Quantity of sand # 5mm = 3.6 Litres Quantity of gravel chips ¼“ = 3.6 Litres Quantity of gravel chips ½“ = 3.6 Litres

(1Cement: 1.5Sand: 1.5gravel ¼“: 1.5gravel ½“) Quantity of cement = 3.7 Litres Quantity of sand # 5mm = 5.6 Litres Quantity of gravel chips ¼“ = 5.6 Litres Quantity of gravel chips ½“ = 5.6 Litres

Steel for one vertical tie & 0ne ring beam

Steel for one vertical tie & 0ne ring beam

6 MS rods (Stirrups) ∅ 10 TS rods ∅

= 0.6 metre = 3.0 metres

6 MS rods (Stirrups) ∅ 10 TS rods ∅

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= 5.7 Litres = 5.7 Litres = 17.2 Litres

= 1.0 metre = 3.0 metres

4.5 BONDS WITH THE BLOCKS 245

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4.6 BONDS WITH THE BLOCKS 295

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4.7 EXAMPLE OF PLAN WITH THE BLOCK 245

MODEL HOUSE FOR TSUNAMI REHABILITATION

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4.8 EXAMPLE OF PLAN WITH THE BLOCK 295

IMPROVED AND REINFORCED AUM HOUSE

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