details about mud

1. MUD CONSTRUCTION TECHNIQUES
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2. CONTENTS:
1.Source Of Soil
2.Types Of Soil
3.Tests
4.Construction Techniques With Soil
5.Guna Vault Roof
6.Nubian Dome
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4. SOIL SOURCE
•Mud required for building can be taken from the plot itself.
•The soil is collected after depth of 60cms only.
•As the top layer is full of organic matter, it isn’t used.
•Below it is sand and clay which are dug out in heaps.
•Do not use hard rock.
•Soil to be used should be devoid of organic matter.
•Top should be replaced after excavating.
SOIL TYPE
• Gravel: Small pieces of stone varying from the size of a pea to that of an egg.
• Sand: Similar small pieces of stone (usually quartz), which are small but each grain, is visible to
the eye.
• Silt: The same as sand except that it is so fine that you cannot see individual grains.
• Clay: Soils that stick when wet - but very hard when completely dry.
• Organic Soil: Soil mainly composed of rotting, decomposing organic matters such as leaves,
plants and vegetable matter. It is spongy when wet, usually smells of decaying matter, is dark in
color and usually damp.
SOIL USABILITY
• Gravel: alone is of no use for mud wall building - the tiny lumps of stone have nothing to bind
them together.
• Sand: similar to gravel, it is of no use for wall making by itself - but if mixed with clay, it is the
ideal mud wall building soil.
• Silt: by itself is also no good for building walls. It will hold together but is not strong.
Furthermore, it will not compact so it is also of no use for pressed blocks or rammed earthwork.
• Clay: can be rammed or compressed but in drying out they often shrink. During the monsoon
they get damp and expand again and crack form.
• Organic Soils: are mainly useless for wall building. 4

5. TESTS
There are two kinds of tests:
Field tests
• Colour tests
• Touch and smell test
• Biscuit test
• Hand wash test
• Cigar test
• Adhesion test
Lab tests
• Sieve test
• Sedimentation test
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6. COLOUR TEST
Procedure
• Observe the colour of soil.
Interpretation
• Deep yellow, orange and red, ranging to deep browns indicate iron content which is good
as building mud.
• Greyish or dull brown, ranging to dirty white indicates more clay.
• Dull brown with slightly greenish colour indicates organic soil.
TOUCH & SMELL
Procedure
• Rub small quantity of dry soil on palm to feel its texture.
• Moisten the soil and rub again.
Interpretation
• Soil that feels course when dry but sticky when wet contains lumps of clay.
• Soil that feels course when dry but gritty when wet contains sand.
• Soil that feels course when dry but little gritty when wet contains silt.
• If the wet soil gives off musty smell then it contains organic matter.
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7. BISCUIT TEST
Procedure
• Make a smooth paste from the soil removing all gravels.
• Mould it into a biscuit of 3cm diameter and 1cm height.
• Leave it to dry and observer for shrinkages or cracks.
• Break the biscuit to noting how hard it is.
Interpretation
• If biscuit cracks or leaves gap from the mould then it contains more clay.
• If its very hard to break then soil contains more clay.
• If it breaks easily and can be crumpled between finger then it has good sand-clay proportion.
• If breaks and reduce to powder then the soil has more sand or silt.
HAND WASH TEST
Procedure
• Play with wet soil till your hands get thoroughly dirty.
• Wash your hands to see how difficult it is to clean.
Interpretation
• If hands get cleaned quickly, then soil contains more sand.
• If it takes little time to clean and feels like flour then soil contains more silt.
• If it feels soapy or slippery and takes time to clean then soil contains more clay.
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8. CIGAR TEST
Procedure
• Make a smooth paste from the soil removing all gravels.
• Roll it on palm to make a cigar.
• Slowly push it outside your palm.
• Measure the length at which it breaks.
Interpretation
• Length below 5cm - too much sand.
• Length above 15cm - too much clay.
• Length between 5cm to 15cm - good mixture of sand and clay.
ADHESION TEST
Procedure
• Make ball out of wet soil.
• Pierce a knife into it and remove.
• Observer the knife after removing.
Interpretation
• If little soil sticks on the knife then it has more silt.
• If lot of soil sticks on the knife then it has more clay.
• If the knife is clean after removal than the soil has more sand.
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9. SIEVE TEST
Procedure
• Pass soil from series of standard sieves set on top of on another with finest sieve at
bottom.
• Observer the soil collected in each sieve.
Interpretation
• Silt will be collected in lowermost sieve.
• Gravels will be collected on top.
• Sand and lumps of clay will be collected in intermediate sieves.
SEDIMENTATION TEST
Procedure
• Take a transparent cylindrical bottle or jar of 1Lt. Capacity.
• Fill it with ¼ soil and ¾ water.
• Shake well and allow it to settle for 30 min.
Interpretation
• Coarse gravels will be settled at bottom, followed by sand, silt and clay on top.
• Measuring the layers will give us the approximate proportions of each content.
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10. STABILISERS
When the available soil is not suitable enough for construction then the soil can be used by manipulating
its composition by adding suitable stabilizers.
• Stabilizing enhances the given property of the soil type.
• Increase Tensile and Shear strength.
• Reduce shrinkage.
Most common and effective stabilizer is Soil itself.
Cement, is the best example of a modern contemporary stabilizer.
Various other indigenous stabilizers include
• Straw
• Plant Juices
• Gum Arabic
• Sugar Or Molasses
• Cow Dung
• Animal Urine
• Tannic Acid
• Oil
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11. Soil suitability and stabilization for CSEB
• A soil contains four components: gravel, sand, silt and clay. In concrete, the binder of gravel and
sand is cement.
• In a soil, the binder is silt & clay. But silt and clay are not stable in water. Thus, the aim of
stabilization is to stabilize silt and clay against water, so as to give lasting properties with the
minimum of maintenance.
• Topsoil and organic soils must not be used. Identifying the properties of a soil is essential to create,
at the end, good quality products. Not every soil is suitable for earth construction and CSEB in
particular.
• But with some knowledge and experience many soils can be used for producing CSEB.
Good soil Gravel 15 % Sand 50 % Silt 15 % Clay 20 %
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12. ADVANTAGES OF CSEB
A local material
• Ideally, production is made on the site itself or in the nearby area. Thus, it will save transportation,
fuel, time and money.
Limiting deforestation
• Firewood is not needed to produce CSEB. This will save forests, which are being depleted quickly in
the world, due to short view developments and mismanagement of resources
Energy efficiency and eco friendliness
• Requiring only a little stabilizer the embodied energy in a m3 can be from 5 to 15 times less than a m³
of fired bricks.
• The pollution emission will also be 2.4 to 7.8 times less than fired bricks.
Flexible production scale
• Equipment for CSEB is available from manual to motorized tools ranging from village to semi industry
scale.
• The selection of the equipment is crucial, but once done properly, it will be easy to use the best
adapted equipment for each case.
Social acceptance
• Demonstrated, since long, CSEB can adapt itself to various needs, from poor income groups to well
off people or government needs. Its quality, regularity
• and style allow a wide range of final house products.
• To facilitate this acceptance, banish from your language “stabilized mud blocks”, when speaking of
CSEB.
• Often people associate in their minds the name mud with poor building material.
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13. DISADVANTAGES OF CSEB
• Proper soil identification is required or lack of soil.
• Unawareness of the need to manage resources.
• Ignorance of the basics for production & use.
• Wide spans, high & long buildings are difficult to do.
• Low technical performance compared to concrete.
• Untrained teams producing bad quality products.
• Over-stabilization through fear or ignorance, implying outrageous costs.
• Under-stabilization resulting in low quality products.
• Bad quality or un-adapted production equipment.
• Low social acceptance due to counter examples (by unskilled people, or bad soil & equipment).
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17. • The Nubian technique traditionally needs a back wall to stick the blocks onto.
• The vault was built arch after arch and therefore the courses were laid almost vertically.
• The binder, about 1-1.5 cm thick, was the silty-clayey soil from the Nile and the blocks used were adobes, the sun
dried bricks.
• The unevenness of the adobes made it necessary to slightly incline the courses, so as to increase the adhesion by
force of gravity.
• This technique has the advantage of allowing one to build vaults and domes without centring.
• This technique with vertical courses has a major disadvantage, which is that the earth glue is very liquid and the
blocks are very thin.
• Therefore the shrinkage of the glue is important and it induces cracks, especially in vaults.
Limit of stability of the horizontal courses
NUBIAN DOME
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18. • When compressed stabilised earth blocks are used to build vaults using this technique, the course can be
absolutely vertical as it is not needed any more to incline the courses for the adhesion.
• The vault, being built with horizontal courses, rises like a corbel which is curved and has courses inclined at the
same angle as the radius of the curve.
• The 6m span semicircular vault cannot be built horizontally anymore, as no force can balance the gravity forces.
• The construction has to go on with vertical courses.
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19. “Guna” in Telugu, is a tapering, burnt clay pipe. The familiar semi-cylindrical
pan tiles are obtained by splitting such pipes vertically into two.
These “Guna” tapering pipes can be socketed into one another forming an arch over a suitably curved shuttering.
A series of such arches make a barrel vault capable of withstanding considerable loads – upto 1 ton/m2.
The top of the roof is given a plaster finish. After joints are filled and topped with plaster, the roof becomes rigid
and waterproof, doing totally without steel or timber.
The cost of this roof works out to Rs. 20/sq.ft. It has the following advantages:
• Air inside the hollow-tiled roof protects from heat and cold. A 10o temperature difference
is observed in slab roof and guna vault roof.
• It has no under structure, yet can bear weight of 1000 kg/m2.
• It is fabricated and ready for use within 3 days.
• Requires no maintenance and has life span of more than 50 years.
• It is not affected by rain, hail or wind.
• Being light in weight (less than 12 kg/sq.ft). the vault roof is safe even in earthquakes.
• Even if the mud walls collapse, the roof remains intact residing on pillars and beams.
GUNA VAULT ROOF
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20. • After construction of brick pillars, ring beams and gable walls, the M.S. trusses are placed in position above the
opposite pillars held with guy ropes and timber poles.
• Now GI pipes (12 mm dia., 10 nos.) are placed on the trusses in the MS rings provided at specific points. They
are supported by gable walls at both ends.
• Guna pipes are now laid dry on this skeleton shuttering in a plug-socket manner, completing the roof ring by
ring.
• Lime/cement mortar is now poured on the roof, trowelling it into the gaps and leaving the top rough to receive
the finishing coat.
• Care is taken to remove the skeleton support within 12 hours to allow natural setting.
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