C.S.E.B. The making…
Soil selection.
Stabilization
Block yard organization.
Comparative study.
Energy effectiveness.
Cost effectiveness.
Advantages.
Limitations.
Methods of construction.
Case studies.
manufacturers.
C.S.E.B. TECHNOLOGY
NEED:
The continued growth in population is going to aggravate the housing situation unless adequate measures are initiated at grass root level. The only constructional materials available in rural areas are bamboo, timber, straw, reeds and mud. About 80% of the total population still dwells in houses made of these above-mentioned materials. These structures are not economically viable because of the maintenance cost due to annual rainfall, storm, flood etc. and susceptibility of attack by insects. The utilization of earth in building construction specially, for rural housing is the oldest but most commonly used by the majority of rural population.
Earth architecture aims to make extensive use of raw earth as the main building material, thereby using a local resource, which can help developing technologies that are energy saving, eco-friendly and sustainable.
5 most important techiniques in earth architecture are:
rammed earth
Adobe
Cob
Wattle & dob
Compressed earth blocks(most popularised)
c.s.e.b. has promoted earth architecture from a traditional craft to a modern technology.
SOIL SELECTION:
A soil is an earth concrete and a good soil for CSEB is more sandy than clayey. It has these proportions:
According to the percentage of these 4 components, a soil with more gravel will be called gravely, another one with more, sand, sandy, others silty or clayey, etc. The aim of the field tests is to identify in which of these four categories the soil is. From the simple classification it will be easy to know what to do with this soil.
Soil identification
A very few laboratories can identify soils for building purposes. But soil identification can be performed by anybody with sensitive analyses. The main points to examine are:
Grain size distribution, to know quantity of each grain size
Plasticity characteristics, to know the quality and properties of the binders (clays and silts)
Compressibility, to know the optimum moisture content, which will require the minimum of compaction energy for the maximum density
Cohesion, to know how the binders bind the inert grains
Humus content, to know if they are organic materials which might disturb the mix.
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. Topsoil and organic soils must not be used. Identifying the properties of a soil is essential to perform, at the end, good quality products. Some simple sensitive analysis can be performed after a short training.
SIMPLE FIELD TESTS
SMELL THE MOIST SOIL FOR THE HUMAS CONTENT:
SMELLS LIKE ROTTEN : A LOT OF HUMAS & ORGANIC MATTER (NOT SUITABLE FOR C.S.E.B.)
SMELLS MUSTY : HUMAS CONTENT (NOT SUITABLEFOR C.S.E.B.)
AGREABLE SMELL : NO HUMAS( SUITABLE FOR C.S.E.B.)
TEST WITH A PRESS AND IMPROVEMENT OF A SOIL:
FOR THIS TEST, WE MUST MAKE 3 COMPRESSED EARTH BLOCKS WITH THE 4 TYPICAL SOILS(ABOUT 25 LITERS PER SOIL).
OBSERVATIONS TO BE RECORDED:
PREPARATION OF THE SOIL.
COMPRESSION & EJECTION.
HUMID STATE OF THE BLOCK.
DRY STATE OF THE BLOCK IN COMPARISION TO THE BLOCK SAMPLE.
RESULTS:
TYPICAL SOILS ARE NOT SUITABLE FOR CEB, BUT THE CLAYEY SOIL IS THE EASIST TO IMPROVE BY ADDING SAND TO DECREASE THE PLASTICITY.
VERY SANDY SOIL CAN ALSO BE IMPROVED WITH MORE CEMENT STABILIZER & LESS COMPRESSION RATIO.
Possible improvements
Gravel soil
sieving ( 12 to 18 mm ) is indispensable to remove the coarse gravel.
A maximum of 15 % by weight of gravel ( max dia 1 cm ) passing the screen
should be allowed.
3. If the soil is too gravely , fine clay powder can be added but it will be too
difficult to mix.
4. Stabilization can be slightly less than 5 – 4 % by weight of cement should
be sufficient.
Sandy soil
Sieving ( 18 mm ) is only required to loosen and aerate the soil .
Do not sieve in very windy areas, especially if the soil is dry .
Stabilization can be 5 % by weight of cement.
Silty soil
A slight crushing might be required .
Sieving ( 12 mm ) is required if the lumps are too big and cohesive .
Adding 15 – 20 % sand might be needed to give more skeleton to the soil.
Stabilization should be 6 % by weight of cement.
Clayey soil
Crushing might be required.
Sieving ( 12 mm ) is required .
Adding 20 - 30 % sand might be needed .
Stabilization should be 5 % by weight of cement.
6-7 % lime can be added for stabilization . Then no sand is required a
combination of cement lime stabilization can give good results.
Ie 2 % cement + 5 % lime.
STABILIZATION:
Soil stabilization
Many stabilizers can be used. Cement and lime are the most common ones.
Others, like chemicals, resins or natural products can be used as well. The selection of a stabilizer will depend upon the soil quality and the project requirements: Cement will be preferable for sandy soils and to achieve quickly a higher strength. Lime will be rather used for very clayey soil, but will take a longer time to harden and to give strong blocks. The average stabilizer proportion is rather low:
PROCESS:
MEASURING:
THE STABILIZATION IS ALWAYS CALCULATED FROM THE WEIGHT OF DRY MATERIAL. AS IT IS IMPOSSIBLE TO MEASURE
DRY WEIGHT ON SITE , ALL THE WEIGHTS MUST BE CONVRETED INTO VOLUME.
THEN IT IS INDISPEN SABLE TO KNOW THE DRY DENSITY OF SOIL WHICH IS THE WEIGHT OF 1 LITRE OF DRY SOIL.
PROCEDURE TO FIND THE DRY DENSITY OF THE SOIL:
TAKE SOME OF THE LOOSE SOIL TO BE TESTED ,DRY IT UNDRE THE SUN OR ON A FRYING PAN. THEN MEASURE 1 LITER
OF THIS SOIL AND WEIGHT IT ON A SCALE. THE WEIGHT FOUND WILL GIVE THE DRY DENSITY.
USUALLY A STBBILIZATION WITH 5% OF CEMENT IS ENOUGH FOR MOST OF THE BUILDINGS.
EACH SOIL IS DIFFERENT IN WEIGHT & IN QUALITY & THEN EACH STABILIZATION IS DIFFERENT. THEN IT IS ADVISED TO
CONDUCT SOME TESTS TO FIND THE BEST MIXING RATIO OF SOIL & CEMENT & SOME TIMES SAND.
TO CONDUCT THESE TESTS , START WITH THE FOLLOWING MIX (BY VOLUME)
1 VOLUME OF CEMENT = 15 TO 20 VOLUMES OF SOIL
THEN AFTER 1 WEEK CURING , THE TRIAL BLOCKS CAN BE EXAMINED AND ,IF NEEDED , CHANGE THE RATIO OF
SOIL/ CEMENT/ SAND.
USE ONLY ¼ OR 1/3 OF A BAG OF CEMENT AT ATIME.:
TO DO IT , TAKE 3 OR 4 BUCKETS & DIVIDE ,IN 1 TIME, A BAG OF CEMENT INTO THEM. THEN ADD THE SOIL
PROPORTIONALLY TO 1 BUCKET.
NOTE:MIXING 1 BAG OF CEMENT AT A TIME WILL GIVE BAD RESULT BECAUSE THE SETTING TIME OF CEMENT WILL BE
SHORTER THAN THAT OF THE TIME NEEDED TO MAKE THE BLOCK.
SOMETIMES A SOIL WHICH IS TOO CLAYEY SHOULD BE MODIFIED BY ADDING SAND , IF THE STABILIZER IS CEMENT.
THEN ,SOME TEST CAN BE CONDUCTED BY ADDING PROGRESSIVELY SAND TO THE SOIL ,SO THAT THE BLOCKS ARE
NEITHER CRACKING NOR CRUMBLING.
THE FOLLOWING GRID CAN SIMPLY BE USED FOR THE MEASURING OF SOIL AND
CEMENT , SO THAT THE % OF CEMENT WILL BE AROUND 5%
BLOCK YARD ORGANIZATION.
TYPICAL LAYOUT:
MANUFACTURING PROCESS:
DIGGING
SIEVING
MEASURING
DRY MIXING
HUMID MIXING
CHECK MOISTURE CONTENT
MOULDING
CHECK THE BLOCK QUALITY
HUMID CURING
FINAL CURING AND SLAKING
SPECIFICATIONS OF THE PRESS 3000 (AURAM):
High output from the automatic opening: 1000 strokes/day. = 125 Blocks/Hour (plain full size blocks)
Handling of the press with 3 men
Mix preparation and block stacking with 4 men
High and adjustable compression ratio from 1.6 to 1.83(1.77 for 9 cm height)
Micro adjustment of compression ratio
Double compression with the folding back lid
Rollers to move the press on site: Only 2 men are needed.
Block height adjustable with ring spacers: 2.5 cm and from 5 to 10 cm (recommended is 9 cm)
Micro adjustment of block height: 0.5mm accuracy
Interchange ability of moulds
Moulds are provided for making 4/4, 3/4 & 1/2 sizes
Self-stability with the adjustable braces
Very easy maintenance with grease nipples and grease gun.
PRESSES AND MOULDS
ADVANTAGES OF C.S.E.B.
A local material
Ideally, the production is made on the site itself or in the nearby area. Thus, it will save the transportation, fuel, time and money.
A bio-degradable material
Well-designed CSEB houses can withstand, with a minimum of maintenance, heavy rains, snowfall or frost without being damaged. The strength and durability has been proven since half a century. But let's imagine a building fallen down and that a jungle grows on it: the bio-chemicals contained in the humus of the topsoil will destroy the soil cement mix in 10 or 20 years? And CSEB will come back to our Mother Earth!
Limiting deforestation
Firewood is not needed to produce CSEB. It will save the forests, which are being depleted quickly in the world, due to short view developments and the mismanagement of resources.
Management of resources
Each quarry should be planned for various utilisations: water harvesting pond, wastewater treatment, reservoirs, landscaping, etc. It is crucial to be aware of this point: very profitable if well managed ? disastrous if unplanned!
Energy efficiency and eco friendliness
Requiring only a little stabilizer the energy consumption 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.
Cost efficiency
Produced locally, with a natural resource and semi skilled labour, almost without transport, it will be definitely cost effective! More or less according to each context and to ones knowledge!
An adapted material
Being produced locally it is easily adapted to the various needs: technical, social, cultural habits.
A transferable technology
It is a simple technology requiring semi skills, easy to get. Simple villagers will be able to learn how to do it in few weeks. Efficient training centre will transfer the technology in a week time.
A job creation opportunity
CSEB allow unskilled and unemployed people to learn a skill, get a job and rise in the social values.
Market opportunity
According to the local context (materials, labour, equipment, etc.) the final price will vary, but in most of the cases it will be cheaper than fired bricks.
Reducing imports
Produced locally by semi skilled people, no need import from far away expensive materials or transport over long distances heavy and costly building materials.
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 most adapted equipment for each case.
Social acceptance
Demonstrated, since long, CSEB can adapt itself to various needs: from poor income to well off people or governments. Its quality, regularity and style allow a wide range of final house products. To facilitate this acceptation, banish from your language "stabilized mud blocks", for speaking of CSEB as the latter reports R & D done for half a century when mud blocks referred, in the mind of most people, as poor building material.
LIMITATIONS OF C.S.E.B.
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 building are difficult to do.
Low technical performances 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).
METHODS OF CONSTRUCTION:
Mortars,
like stabilizers, can be made using various proportions of cement and lime. A good environmentally sound mortar for PEBs can be made using 1 part Hydraulic Lime, 4 parts sand and enough water to make the mortar workable.
Pre-packaged mortars, like Brixment brand type-N Coplary Cement, can be used to make a very strong but expensive and environmentally costly mortar. A homemade version of this mortar can be made by mixing 1 part Portland Cement with 6 parts sand and enough water to make workable.
Another strong mortar can be made by combining 1 part Portland Cement, 4 parts lime, 32 parts sand and water.
When mixing mortar, mix all dry ingredients thoroughly before adding water. After laying up bricks in mortar, keep the mortar moist for a day or so.
Mortaring
Mortar for blocks must be applied to the entire surface of the block, as opposed to ribbon mortar beds often used with conventional brick. Full surface mortaring allows for maximum compressive strength. The same soil used in block making, mixed with water to form a slurry, is usually used as a mortar for binding blocks together into floors and walls. Cement can be added to the mortar mix, but this increases the cost. The main advantage of cement mortar is its quick drying speed.
Design Methods
Block size can be varied easily to accommodate a variety of designs. Walls can be sculptured, rounded, or formed into keystone arches to create custom effects. Relatively unskilled labor can be utilized in construction with compressed earth and caliche block.
Design of structural walls using caliche or soil material block must take into account wall height and thickness, size of block, insulation value, and the desired style and finish. Wall height-to-thickness ratio must be adequate for stability.
The relatively low insulation value of soil or caliche block may make additional insulation necessary. The most cost effective wall thickness for insulation value is 12 inches.
Soil or caliche block structures need not have the "pueblo" style if this is not desired. Many architectural styles are possible. A bond or collar beam is necessary if the roof is supported by the walls. This will serve to spread the loads over the entire wall, and stabilize the tops of the walls from horizontal movement.
Vertical reinforcement is difficult with solid block walls, but can be accommodated with the use of reinforced concrete columns at corners, wall openings, and at intervals in the wall. In this case, the soil block becomes an infill panel. Alternatively, walls made more than one block thick may have internal reinforcing between blocks, and have additional insulation between panels. With this method, care must be taken to ensure that the lower block courses are completely dry before additional courses are added.
Soil blocks are typically stuccoed to prevent them from getting wet. Clear finishes may be applied on the interior.
Particular 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 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)
RESEARCHES RELATED TO C.S.E.B.
The following technologies have been mastered and are disseminated since years:
Stabilised rammed earth foundations
Rammed earth walls, rammed manually
Composite plinth – step plinth with CSEB and plinth beam cast in U shaped CSEB
Wide variety of compressed stabilised earth blocks (15 modules available today)
Stabilized earth mortars and plasters
Composite columns – Round hollow CSEB with reinforced cement concrete
Composite beams and lintels – U shaped CSEB with reinforced cement concrete The following technologies are still under research and they will be disseminated only once mastered:
Composite blocks (earth, fibres and stabilizer)
Alternative stabilizers to cement (“homeopathic&rdquo milk of lime and alum)
Alternative water proofing with stabilized earth (soil, sand, cement, lime, alum and tannin from the juice of a seed)
CASE STUDIES:
VISITORS CENTRE, Auroville , India.
ARCHITECT: SUHASINI IYER
. CONSTRUCTED IN YEAR 1998 WITH
GRANDS FROM HUDCO &
FOUNDATION OF WORLD EDUCATION.
.POPULAR & PLESENT PLACE FOR
VISITOR & AUROVILIANS ALIKE.
.A.V.B.C. HAS DEMONSTRATED RITCH
POTENTIAL OF ALTERNATIVE TECHNOLOGIES AND ENERGY SAVING MATERIALS IN IT.
.DESIGNED WITH EMPHASIS ON NATURAL LIGHTING & VENTILATION ALONG WITH RENEWABLE ENERGY SOURCES.
.COMPRISES OF INFORMATION DESK, EXHIBITATION SPACESES, CAFETERIA,HANDICRAFT SHOP ,BOOK SHOPS ETC. SPECIALLY DESIGNIED FOR VISITORS FROM ALL OVER THE WORLD.
SPECIAL FEATURES:
PREFABRICATED FERROCEMENT ELEMENTS WERE USED FOR DOORS & OVERHANGS,THEREBY DOING AWAY WITH THE USE OF WOOD.
A 4-METRE GRID USING LOAD-BEARING PILLARS AND ARCHED OR COBBLED OPENINGS WAS MADE WITH C.S.E.B. TO REDUCE THE COSTS.
SOLAR, WIND, &BIOMASS ENERGY, WATER MANAGEMENT &RECYCLING TECHNIQUES, MUD AND FERROCEMENT TECHNOLOGY , AND RECLAMATION & AFFORESTATION WERE ALL INTEGRATED IN THE PROCESS.
C.S.E.B. FOR DOMES & PREFABRICATED FERROCEMENT CHANNELS WERE CONSIDERED AS THE BEST SOLUTIONS FOR ROFFING.
LIMIT THE USE OF CEMENT & CONCRETE.
RE HABILATED HOUSE IN GUJARAT AFTER KUTCH EARTHQUAKE.
Today Compressed Earth Blocks (CSEB) rival the finest standard bricks available in terms of strength and durability; are highly cost-effective and environmentally-friendly; can be safely used for construction of multi-storey buildings; and lend themselves to a variety of creative and aesthetically pleasing effects.
manufacturers.
RESEARCH ORGANISATIONS:
CRATerre EAG AUROVILLE BUILDING CRNTRE
CBRI (ROORKEE) MUD VILLAGE SOCIETY (DELHI)
ASTRA (BANGLORE) HUDCO
TYPOLOGY OF BLOCKS:
The Auram press 3000 can presently produce 16 different types of Compressed Stabilised Earth Blocks.
These series are available:
Plain square blocks
Plain rectangular blocks
Round blocks
Hollow square blocks
Hollow rectangular blocks
Hollow square interlocking blocks
Hollow rectangular interlocking blocks
Plain square interlocking blocks
Plain rectangular interlocking blocks
Various special blocks
