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DETAILED PROJECT REPORT

FOR

PRODUCTION OF COMPRESSED STABILIZED

EARTHEN/ SOIL/ MUD BLOCK

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CONTENTS

INTRODUCTION ...................................................................................................................... 3

MATERIALS ............................................................................................................................. 4

BROAD GUIDELINE TO SELECT OR MODIFY SOIL FOR THE PRODUCTION OF CSEB: .............. 4

PRODUCTION STAGES: ........................................................................................................... 5

DIMENTIONS AND TOLERANCES: ........................................................................................... 8

BLOCK PRESS MACHINES: ..................................................................................................... 10

TYPICAL BLOCK-YARD ORGANISATION: ................................................................................ 10

COST BREAK UP OF CSEB ...................................................................................................... 11

ADVANTAGES AND LIMITATIONS: ........................................................................................ 12

SPECIFICATIONS FOR COMPRESSED STABILIZED EARTH / SOIL/ MUD BLOCKS: .................. 13

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INTRODUCTION

Earth as a construction material has been used for thousands of years by civilisations all

over the world. It is the most abundant building material known and available in majority

of the locations. The ttraditional soil construction methods in the country are cob

(mixture of straw, gravel and clay), wattle and daub - (coarse basket work of twigs woven

between upright poles and plastered with earth) and adobe – (roughly moulded, sundried

clay bricks). The main drawback of these types of earth construction is their lack of

durability, further research is required so as to improve their quality.

Compressed Stabilized Earth Block (CSEB) is one of such technology, in which blocks are

made by compressing earth/ soil mixed with Suitable stabilizer (cement/ lime) at optimum

moisture content by simple mechanical means. Densification of soil at Optimum moisture

content and use of stabiliser make CSEB durable and it does not soften due to action of

the water.

Production of CSEB generates employment to the unskilled labour. Baking is not required

thus it is environmental friendly practice. This blocks can be used in construction of

houses, government buildings, Toilets, etc.

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MATERIALS

Materials required for construction of Compressed Stabilised Earth Blocks (CSEB) are as

follows:

Cement: The cement shall confirm to either IS 269 or IS 1489 (Part-1) or IS 8112 or IS

12269.

Lime: Lime shall confirm to IS 712

Sand: The sand to be used for diluting the soils shall be either natural river sand, crushed

stone sand or crushed gravel sand confirming IS 383. It should be free from any type of

salt/ chemical and organic matter.

Soil: Soil shall be of the quality suitable for the production of stabilized soil blocks.

Generally, soil contains clay minerals and inert particles such as silt and sand. The

percentage and type of clay mineral controls the characteristics of soil. In majority of the

cases the clay mineral content of the soil has to be controlled and adjusted by diluting the

soil with sand, in order to make the soil suitable for CSEB.

Water: The water to be used in the manufacture of blocks shall not be detrimental to its

durability.

BROAD GUIDELINE TO SELECT OR MODIFY SOIL FOR THE PRODUCTION OF CSEB:

The soil or soil-sand mixture meeting the specification given in Table-1 may result in

production of good quality stabilized blocks. The recommended values of stabilizer to clay

ratio for expansive and non-expansive soil have been given in Table-2.

Table 1: Recommended specification for soil or soil-sand Mixture

S. No. Details Limiting value

1 Granular composition of soil-sand mixture:

a) Clay fraction (< 0.002 mm) 5%-18%

b) Silt fraction (0.002-0.075mm) 10%-40%

c) Sand fraction (0.075-4.75mm) 50%-80%

d) Gravel fraction (4.75-6mm) 0%-10%

2 Liquid limit Less than or equal to 30%

3 pH 6.5 – 8.5

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Table 2: Recommended Stabilizer to Clay Ratio for Different Types of Soils

S. No. Type of soil Stabilizer to Clay Ratio (by

Weight)

1 For soils having non-expansive clay minerals

(for example, kaolinite, illite, etc.)

More than or equal to 0.40

2 For soils having expansive clay minerals (for

example, montmorillonite)

More than or equal to 0.75

Note: Stabilizer content should be more than or equal to 5% (by Weight)

Use of soil containing expansive clay minerals such as montmorillonite requires lime as a

stabilizing additive to manufacture CSEB. Acidic soils having pH less than 6.5 can be

stabilized with addition of 1 to 2 percent calcium hydroxide (lime) by weight in addition to

cement. Soil containing excessive silt fraction can lead to CSEB having very low green

strength for handling during block manufacturing process. In such situations, coarse gravel

or coarse sand fraction can be added to the soil to overcome the problem.

PRODUCTION STAGES:

Stages involved in production of CSEB are as follows:

1) Site Identification for Borrow pit:

The borrow pit is a source of raw soil for the production of CSEB. It should not be too far

from the production site in order to reduce transportation costs of the raw material.

Sufficient soil must be available from the borrow pit to satisfy the proposed scale of

production. Before any major action takes place, soil samples from trial holes must always

be taken to check the adequacy of the soil and to be able estimate available amounts. Soil

composition can vary greatly even within a small area so several test holes should be dug

to give a full picture of the type of the soil within a borrow pit.

Laboratory analysis of the raw material is always necessary for large-scale production of

compressed stablised earth blocks. Before going for it, Simple field tests can be performed

to get an indication of the composition of the soil sample. Such tests are discussed briefly

below.

Smell test: Smell the soil immediately after it has been sampled. If it smells musty it

contains organic matter. This smell will become stronger if the soil is heated or wetted. Soil

containing organic matter is not suitable for production of compressed stabilised earth

blocks.

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Touch test: Remove the largest grains and crumble the soil by rubbing the sample between

the fingers and the palm of the hand. If it feels rough and has no cohesion when moist the

soil is sandy. If it feels slightly rough and is moderately cohesive when moistened the soil is

silty. If, when dry, it contains lumps or concretions which resist crushing, and if it becomes

plastic and sticky when moistened the soil is clayey.

Sedimentation test: The tests mentioned previously make it possible to form a general

idea of the texture of the soil and the relative particle sizes of the different fractions. To

obtain a more precise idea of the nature of each soil fraction, a simplified sedimentation

test can be carried out in the field. The apparatus required is straight forward: a

transparent cylindrical glass bottle with a flat bottom and a capacity of at least one litre,

with a neck wide enough to get a hand in and a lid to allow for shaking. Fill the bottle to

one-third with clean water. Add approximately the same volume of dry soil passed through

a 6mm sieve and add a teaspoonful of common salt. Firmly close the lid of the bottle and

shake until the soil and water are well mixed. Allow the bottle to stand on a flat surface for

about half an hour. Shake the bottle again for two minutes and stand on level surface for a

further 45 minutes until the water starts to clear. The finer particles fall more slowly and as

result will be deposited on top of the larger size particles. Two or three layers will emerge,

with the lowest layer containing fine gravel, the central layer containing the sand fraction

and the top layer containing silt and clay. The relative proportions, and hence percentages,

of each fraction can be determined by measuring the depth of each layer.

Image 1: Sedimentation test

Image 2: Adhesion test

With field tests and laboratory tests, suitable site for borrow pit to be identified as per soil

specifications given in table-1.

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2) Soil Preparation:

In order to have uniform soil, it is necessary to crush it so that it can pass through a 6mm mesh

sieve. It is then to be sieved through a 6mm sieve to remove gravel, lumps of clay, roots,

etc. If the soil gradation is to be changed by adding sand/ quarry dust or clayey soil, this

addition is to be done now. The operation of block making is always carried out in batches.

The batch size can generally vary between 25 to 50 blocks per batch, for manually

operated block press machine. The quality of mixing may suffer if a larger batch size is

attempted. For larger batch sizes, mechanical mixing may have to be thought of.

3) Mixing of soil and stabilizer:

As per table-2 quantity of stabilizer for given type of soil is to be ascertained. In order to

achieve satisfactory mixing, the selected soil quantity must be spread as a thin layer of

about 15cm in thickness. The appropriate stabilizer quantity now spread as a thin layer on

the soil. The soil and stabilizer are now mixed initially with spade and subsequently with

hand. The mixing is completed when the mixture attains a uniform colour.

4) Addition of Moisture:

At the outset, the amount of moisture to be added may be estimated approximately. A

sandy soil will usually need 10% to 12% water for optimum moisture content (OMC).

Water for optimum moisture content is to be sprinkled on the soil stabilizer mixture which

is spread thinly on level ground. The soil and water are mixed thoroughly by hand the

process is repeated with remaining water. The adequacy of moisture is now checked by

making a ball out of moist soil. If a ball can be made without the soil sticking to the hand

the moisture content is optimum. If ball cannot be made, the mixture is below OMC and

small quantity of water may be added and again checked for OMC. The moist soil plus

stabilizer mixture is now ready for block pressing.

5) Block pressing:

The Block press machine should be anchored in position. The moist mixture of soil and

stabilizer may now be taken in a scoop and weighed. The weight of the soil should be such

that desired block density is achieved. The stabilized soil mixture is now poured in to the

mould through quick up and down motion of scoop. It is to be compacted in the block

press machine to a CSEB block.

6) Block ejection and stacking:

The block is to be ejected from the block press machine, removed from the mould and

taken for stacking. The machine is now ready for next block. Fresh blocks may be stacked

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on a leveled ground under polythene sheet to avoid quick loss of moisture. The stacking

yard should be as close to the machine as possible. The blocks may be stacked one above

the other up to six layers.

7) Curing of the blocks:

The blocks must be cured for 21 days by gently sprinkling moisture. Strawn or Gunny bags

may be used to cover stack. Alternatively block may be cured for 7 days in stack and then

used for wall construction. The further curing for 14 days must be pursued in the wall

wherein it is often necessary to cure mortar as well.

DIMENTIONS AND TOLERANCES:

The Modular size of stabilised Earth blocks shall be as follows:

Length (mm) Width (mm) Height (mm)

290 90 90

290 140 90

240 240 90

190 90 90

190 90 40

The dimensions of the units are so designed that taking account of mortar joints, they will

produce wall lengths which will confirm to the principles of modular co-ordination.

The following non-modular sizes of the bricks may also be used:

Length (mm) Width (mm) Height (mm)

305 143 100

230 190 100

305 143 100

230 190 100

230 105 75

230 105 100

Tolerances: The maximum variation in the dimensions of the units shall not be more than

+/- 2mm.

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Frog: Each block may have frogs on both the bed faces in the form of depression of

rectangular or square shape with depth not excceding 10mm. In such cases, the area of the

frogs on each bed face shall be restricted to 25 percent of the surface area and it is

preferable to have at least one frog on either face.

PHYSICAL REQUIREMENTS:

Sr.

No. Parameter Requirements

1 Dry Density of the Block The dry density of the blocks, being the

average of three specimens, when determined

in accordance with the procedure prescribed

in Annex C of IS1725, shall not less than 1750

kg/m^3

2 Compressive strength The minimum average compressive strength

of blocks when determined in the accordance

with the procedure described in IS3495 (Part-

1) shall 3.5 Mpa (35kg/cm^2)

The compressive strength of any individual

block shall not fall below the minimum

average compressive strength by more than

15%.

3 Water absorption The average water absorption of the blocks

when determined in accordance with the

procedure prescribed is IS3495 (Part2) after

immersion in cold water for 24hr shall not be

more than 18 percent by weight

4 Linear expansion on saturation

of the blocks

The linear expansion on saturation of the

blocks, being the average of three specimen,

when determined in accordance with the

procedure described in Annex D of IS1725,

shall not exceed 0.10%

5 Weathering The maximum loss of weight , being the

average of three specimens, when determined

in accordance with the procedure described in

Annex E of IS 1725, shall not exceed 3%

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BLOCK PRESS MACHINES:

Suggestive block press machines suitable for CSEB production under MGNREGS with their

suppliers is given below.

Mardini Block Press

Maheemaya, 65/108,

Bilekahalli, Bannerghatta

Road, Bangalore-560076

e-mail:

mrinmayee8819@gmail.com,

gramavidya@gmail.com

Phone: (080)2658 2970

Auram Press 3000

Aureka, Aspiration,

Auroville, Tamil Nadu –

605101

e-mail:

aureka@auroville.org.in

Phone: (0413)2622278/

2622134/ 2622651

Fax: (0413) 2622274

TARA machines and Tech

services Pvt. Ltd.

B-32, TARA Crescent, Qutab

Institutional Area,

New Delhi - 110 016

e-mail:

info@taramachines.com

Cell No:

09599222036, 09599787054

TYPICAL BLOCK-YARD ORGANISATION:

Persons required at different stages of the block production, with manually operated block

press machine, may be given as:

Sr.

No. Stages of block production Number of persons required

1 Soil Preparation: 2 to 4 persons

2 Mixing of soil and stabilizer 2 persons

3 Addition of Moisture 2 persons

4 Block pressing: 3 persons

5 Block ejection and stacking: 1 person

6 Curing of the blocks: 1 person

Total 11-13 persons

Note: Data given above is suggestive. Actual number of person required, depends on Type

of block press machine, type of soil, transportation distance for raw material and block

produced, etc.

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Key words for the organisation of the block-yard:

• Reduce the distance of transportation

• Optimise the ratio output / number of workers to get the best efficiency.

• Organise the block-yard as close as possible from the site.

• Organise the store room as close as possible from block yard.

• Organise the final stacking area as close as possible from the block yard.

• It is preferable to have linear organisation but circular one can also be suitable.

COST BREAK UP OF CSEB

1 Fixed capital Unit Cost (Rs)

Land, Shed and Storage 500 sqm 300,000.00

Submersible with pump 1 No 50,000.00

Pressing machine & all accessories 1 No 120,000.00 (Minimum)

Other miscellaneous Lum sum 600,00.00

Total 5,30,000.00

2 Recurring expenditure for 1000 blocks of size 230X105X75mm

Item Qnty Unit Rate (Rs) Cost (Rs)

Manpower per day: 13.00 Nos 160 2,080.00

Cement 4.00 Bag 320 1,280.00

Soil 4.00 M3 150 600.00

Sand /quarry dust 0.40 M3 200 80.00

Lime 4.00 KG 12 48.00

Water 600.00 Liters 1 600.00

Press machine charges and interest rate

per day 677.00

Total 5,365.00

3 Cost analysis ratio

Production capacity 1000/ Per Day

Per Day Expenditure Rs 5365.00

Cost for each Brick Production Rs 5.37

4 Wage Material ratio

Unskilled wage component Rs 2080.00 (44.37%)

Material component Rs 2608.00 (55.63%)

Note: In general the labour cost (which includes the soil digging, its preparation and the

block making) is highest. Therefore if the productivity decreases, the cost of the block will

increase proportionally a lot. In general, to reduce the cost of the block one should optimize

the productivity of workers.

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ADVANTAGES AND LIMITATIONS:

Advantages:

• Can be very cost effective, especially when the blocks are produced at the site of use

• Soil is an easily available resource in rural housing

• Provides good thermal comfort

• Provides aesthetical wall finish, no plaster required

• Creates additional local employment in block production

• Can be made with locally available earth which makes it cost effective.

• Thermally comfortable, aesthetically pleasing and one of the most environment

friendly alternatives for wall construction.

Limitations:

• Requires a good understanding of the type of soil available for block production and

how it can be improved/ stabilized.

• Availability of soil in adequate quantity from a single source, can be a limitation.

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SPECIFICATIONS FOR COMPRESSED STABILIZED EARTH / SOIL/ MUD BLOCKS:

IS 1725: Stabilised soil blocks used in general building construction- Specification

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