EART-SOIL AS BUILDING MATERIAL

EART-SOIL AS BUILDING MATERIALThe thing that hit me in the eye, right from the beginning, was that an enormous amount of use was made of mud! The first thing I discovered was that mud is one thing in one place and a different thing in another. It is used for different purposes and is used in different ways! There are different techniques of sticking it together and making it into a wall or whatever. This varied considerably, even sometimes in a matter of a few miles, from one district to anotherLaurie Baker

EART-SOIL AS BUILDING MATERIAL

Mud as a construction material has been extensively used since Neolithic times.

Mud construction is mainly found in places which arerelatively dry and have mud in abundance.EART-SOIL AS BUILDING MATERIAL

WE PREJUDICED?Why isnt mud considered modern?Is it true that mud is not as strong as cement and steel?Are concrete and steel perceived to be better simply because they are seen to be the result of modern scientific and technological processes?Is this a problem of mud itself or is this merely a problem of the modern mind?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 isnt 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 TYPES

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.TESTS

Field testsColour testsTouch and smell testBiscuit testHand wash testCigar testAdhesion testLab testsSieve testSedimentation testCOLOUR TEST

Procedure -Observe the colour of soil.InterpretationDeep 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

ProcedureRub small quantity of dry soil on palm to feel its texture.Moisten the soil and rub again.InterpretationSoil 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 matterBISCUIT TEST

ProcedureMake 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 observe for shrinkages or cracks.Break the biscuit to noting how hard it is.InterpretationIf 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

ProcedurePlay with wet soil till your hands get thoroughly dirty.Wash your hands to see how difficult it is to clean.InterpretationIf 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.

CIGAR TEST

ProcedureMake 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.InterpretationLength below 5cm - too much sand.Length above 15cm - too much clay.Length between 5cm to 15cm - good mixture of sand and clay.ADHESION TEST

ProcedureMake ball out of wet soil.Pierce a knife into it and remove.Observe the knife after removing.InterpretationIf 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.SIEVE TEST

ProcedurePass soil from series of standard sieves set on top of on another with finest sieve at bottom.Observer the soil collected in each sieve.InterpretationSilt will be collected in lowermost sieve.Gravels will be collected on top.Sand and lumps of clay will be collected in intermediate sievesSEDIMENTATION TEST

ProcedureTake a transparent cylindrical bottle or jar of 1Lt. Capacity.Fill it with soil and water.Shake well and allow it to settle for 30 min.InterpretationCoarse 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.STABILISERSWhen 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.

STABILISERSMost common and effective stabiliser is Soil itself.Cement, is the best example of a modern contemporary stabiliser.Various other indigenous stabilisers includeStrawPlant JuicesGum ArabicSugar Or MolassesCow DungAnimal UrineTannic AcidOil

STABILISERSMost common and effective stabiliser is Soil itself.Cement, is the best example of a modern contemporary stabiliser.Various other indigenous stabilisers includeStrawPlant JuicesGum ArabicSugar Or MolassesCow DungAnimal UrineTannic AcidOil

EARTH TECHNIQUES

EARTH TECHNIQUESCobPise or Rammed earthAdobePressed bricksWattle and daub methodSYSTEMS OF BUILDINGCOB is good for anything except height. It is particularly good for curved or round walls.PISE OR RAMMED EARTH is strong and ideal for solid, squat, single storey houses.ADOBE or SUN DRIED BRICKS can easily cope with two storey houses.PRESSED BRICKS smooth and very strong and can build three storey.WATTLE & DAUB is elegant and fine for Seismic Zones.

COBCob or cobb or clom (in Wales) is a building material consisting of clay, sand, straw, water, and earth, similar to adobe. Cob is fireproof, resistant to seismic activity,[1] and inexpensive. It can be used to create artistic, sculptural forms and has been revived in recent years by the natural building and sustainability movements.The walls of a cob house were generally about 24inches thick, and windows were correspondingly deep-set, giving the homes a characteristic internal appearance. The thick walls provided excellent thermal mass which was easy to keep warm in winter and cool in summer.Walls with a high thermal mass value act as a thermal buffer inside the home.The material has a long life span even in rainy climates, provided a tall foundation and large roof overhang are present.

COBWith only a little water to form a very stiff mud, a large lump is roughly moulded into the shape of a huge elongated egg.The usual size is anything between 12 to 18-inches, (30 to 40-cm) long and about 6-inches (15-cm) in diameter.A row of these cobs of mud are laid neatly side-by-side - preferably somewhat pressed together.Then another row of cobs is laid on top.When three or four courses have been laid, one above the other, the sides are smoothed over so that the holes and cracks disappear.Openings for doors, and windows are a problem, which can be solved by using temporary vertical planks or shuttering.Another very simple shuttering for openings is to use empty kerosene tins.

RAMMED EARTH

Rammed earth, also known as taipa[1] (Portuguese), tapial (Spanish), and pis (de terre) (French), is a technique for building walls using the raw materials of earth, chalk, lime and gravel. It is an ancient building method that has seen a revival in recent years as people seek more sustainable building materials and natural building methods. Rammed-earth walls are simple to construct, incombustible, thermally massive, strong, and durable. They can be labour-intensive to construct without machinery (powered tampers), however, and they are susceptible to water damage if inadequately protected or maintained. The second method has developed from the cob wall so as to standardize or regularize the thickness of the wall.

RAMMED EARTH

Building a rammed-earth wall involves compressing a damp mixture of earth that has suitable proportions of sand, gravel and clay (sometimes with an added stabilizer) into an externally supported frame or mould, creating either a solid wall of earth or individual blocks. Historically, such additives as lime or animal blood were used to stabilize the material, whilst modern construction uses lime, cement or asphalt emulsions. Some modern builders also add coloured oxides or other items, such as bottles or pieces of timber, to add variety to the structure.It is also an attempt to increase the strength of the wall by ramming it. It is known as the Rammed Earth method.Two parallel planks are held firmly apart by metal rods and clips or bolts, or by small crosspieces of wood.Stiff mud is thrown in between these two planks and rammed down with either a wooden or metal ramrod.

RAMMED EARTH

When one section is completed and hard, the two boards are moved along and the process is repeatedThe two planks are then raised up and a second course of rammed earth is repeated over the first.The compression strength of the rammed earth increases as it cures; it takes some time to dry out, as much as two years for complete curing. Exposed walls should be sealed to prevent water damage.The compressive strength of rammed earth can be up to 4.3MPa (620psi). This is less than that of concrete, but more than strong enough for use in domestic buildings.[3] Indeed, properly built rammed earth can withstand loads for thousands of years, as many still-standing ancient structures around the world attest.[4] Rammed earth using rebar, wood or bamboo reinforcement can prevent failure caused by earthquakes or heavy storms. Adding cement to clay-poor soil mixtures can also increase a structure's load-bearing capacity

Holy Cross Episcopal Church) in Stateburg, South Carolina,

EDEN PROJECTADOBEAdobe is a natural building material made from sand, clay, water, and some kind of fibrous or organic material (sticks, straw, and/or manure), which the builders shape into bricks using frames and dry in the sun. Adobe buildings are similar to cob and mudbrick buildings. Adobe structures are extremely durable, and account for some of the oldest existing buildings in the world. In hot climates, compared with wooden buildings, adobe buildings offer significant advantages due to their greater thermal mass, but they are known to be particularly susceptible to earthquake damage.

ADOBEBuildings made of sun-dried earth are common in the West Asia, North Africa, West Africa,[3] South America, southwestern North America, Spain CompositionAn adobe brick is a composite material made of clay mixed with water and an organic material such as straw or dung. The soil composition typically contains clay and sand. Straw is useful in binding the brick together and allowing the brick to dry evenly.{{[9] }} Dung offers the same advantage and is also added to repel insects. The mixture is roughly half sand (50%), one-third clay (35%), and one-sixth straw (15%) by weight.

Bricks are made in an open frame, 25cm (10in) by 36cm (14in) being a reasonable size, but any convenient size is acceptable. The mixture is molded by the frame, and then the frame is removed quickly. After drying a few hours, the bricks are turned on edge to finish drying. Slow drying in shade reduces cracking.

ADOBEThe same mixture to make bricks, without the straw, is used for mortar and often for plaster on interior and exterior walls. Some ancient cultures used lime-based cement for the plaster to protect against rain damageReinforcement can include manure, straw, cement, rebar or wooden posts. Experience has shown straw, cement, or manure added to a standard adobe mixture can all produce a stronger, more crack-resistant brickAn adobe wall can serve as a significant heat reservoir due to the thermal properties inherent in the massive walls typical in adobe construction.

ADOBEBlocks shall be kept covered with air tight polythene sheets for first 48 hrs with relative humidity up to 100.Polythene sheets shall be removed after 48 hrs and the blocks shall be kept in shaded area like having enough air circulation.Sprinkle water over blocks daily, as many times needed, during 28 days.Write date of production on block corner.Cover stacks top with coconut leaves or any other cover to avoid direct sunlight.Principle is that blocks shall not dry for 4weeks.

Image:Iran, Bam.COMPRESSED EARTH BLOCKCompressed Earth Block often referred to simply as CEB, is a type of manufactured construction material formed in mechanical press that forms an appropriate mix of dirt, non-expansive clay, and an aggregate into a compressed blockCEB blocks are installed onto the wall by hand and a slurry made of a soupy version of the same dirt/clay mix, sans aggregate, is spread or brushed very thinly between the blocks for bonding.

COMPRESSED EARTH BLOCKThe advantages of CEB are in the wait time for material, the elimination of shipping cost, the low moisture content, and the uniformity of the block thereby minimizing, if not eliminating the use of mortar and decreasing both the labor and materials costs.CEB can be pressed from humid earth. Because it is not wet, the drying time is much shorter. Some soil conditions permit the blocks to go straight from the press onto the wall. A single mechanical press can produce from 800 to over 5,000 blocks per day, enough to build a 1,200 square feet (110m2) house in one day. The Liberator, a high performance, open source CEB press, can produce from 8,000 to over 17,000 blocks per day.

WATTLEANDDAUBWattle and daub method is an old and common method of building mud structures.There bamboo and cane frame structure that supports the roof.Mud is plastered over this mesh of bamboo cane and strawsDue to excessive rainfall the Wattle and Daub structures gets washed off.However, the mesh of cane or split bamboo remains intact and after the heavy rain is over the mud is plastered on again.

EARTHBAG CONSTRUCTIONThis method was developed from the bunkers made by the militaryThe basic construction method begins by digging atrench.Rows of woven bags (or tubes) are filled with available inorganic materialAfter the foundation is laid, each successive layer will have one or more strands ofbarbed wireplaced on top.The weight of this earth-filled bag pushes down on the barbed wire strands, locking the bag in place on the row below.The most popular type of bag is made of wovenpolypropylene.Organic/natural materials such ashemp,burlapor other natural-fiber bags (like "gunny sacks") can be used.

FOUNDATIONOften it is feasible to build the walls of a home on mud, but some more solid material is needed for the foundation and basement.If stone is locally available it can be used.There are times when the topsoil may be soft and useless but there may be reasonable harder subsoil capable of carrying the weight of a single storey mud house. In this situation remove the soil from the trench you would normally dig for a stone or brick foundation.Slightly dampen the excavated soil and then replace a part of it to fill the trench about 6 to 9-inches. Ram this very hard - then repeat until the trench is full.If there is bamboo is available, it can be used to make narrow rafts of split bamboo. Having done the first 6-inches infilling and ramming, a raft of bamboo strips is laid all around.

MORTARSUITABLE MORTAR FOR MASONRYStabilised Earth Mortar is best suited for masonry using mud blocks.Mud mortar shall be stabilised 1.5 times more than the mud blocks.Add course sand (0.2 to 2mm) to reduce shrinkage.Prepare plastic mix rather than dry mix.Ideal mix = soil suitable for mud block + 40% to 50% of sand by weight + 7.5% cement.

MORTARTest the mortar before useProcedureStart with a mix of 1 vol. Cement + 6 vol. Soil + 6 vol. Sand.Apply a layer of 1cm mortar on a block soaked in water and let it dray in shade.Observe the mortar for cracks.InterpretationIf cracks appear, reduce the soil and increase the sand proportion.1 cement + 5 soil + 7 sand.If mortar is too crumbly, increase the soil and reduce the sand proportion.1 cement + 7 soil + 5 sandnt.

TREATMENT AGAINST TERMITESMud is the natural home of termites so in areas where they are common the same precautions have to be taken as in all buildings to prevent their moving up into the walls and eating wooden frames etc.A one-inch thick layer of mortar (one part of cement to 3-parts of sand) can be laid all over the top of the basement wall before building the mud walls above it. This is helpful in keeping out both termites and damp.

TREATMENT AGAINST TERMITESEven better is to construct an apron of burnt brick or stone (or it can be rammed earth) all round the building (to prevent damage to the walls by splashing, of rain water) and this too can be plastered over with a rich cement mortar.Any thin sheet metal may be laid over the basement wall with a 3-inch downward projection before starting to build the superstructure mud wall above. This is expensive but very effective.There are various chemicals on the market, which can be used.

WATER

Water and dampness are one of the major problems for mud as construction material.The best way of protecting any wall from either rain or sun is to have a good big overhang to your roof.The sloping, or pitched roof is better because the walls need not be so high as for a flat roofed house.Provide trenches round the house to receive dripping water and drain it away.