Historically, earth has been the most widely known and used building material in construction and probably has been the most important of all building materials (Legget, 1960). Stabilized soil bricks are cost effective and energy efficient alternative materials to the normal burnt clay bricks used for construction of buildings. Actually, most developing countries are facing a real housing deficiency (Harison & Sinha, 1995). Therefore, there is an urgent need to construct and build houses that are more durable at a low cost. A striking contrast between stabilized soil brick and conventional brick is the energy consumed during the production process and carbon emission. Stabilized soil brick creates 22kg co2/tone compare to that of concrete blocks (143kg co2/ton), common fired clay bricks (200kg co2/ton) during production. In average, cement stabilized soil bricks consumed less than 10% of the input energy as used to manufacture similar fired clay and concrete masonry unit. The technique to enhance natural durability and strength of soil defined as soil stabilization. The demand for sustainable building material at low cost is growing as social, economic and environmental issues evolve in today’s society. Recent reports indicated that, about half of the words population are still living in earth buildings (mc henry, 1984; EBAA, Australia). From the literature the best soil composition for soil-cement is 75% sand, 25% silt & clay, of which more than 10% is clay.

Compressive strength is the capacity of a material to withstand axially directed pushing forces. When the limit of compressive strength is reached, materials are crushed. Compressive strength = max load at failure (N)/avg. area of bed face(mm2) In general, compressive strength testing procedures for earth bricks follow those developed for fired clay and concrete masonry units.(ASTM,1984; British standards institution 1985; standards Australia 1997). Individual specimens are tested in uniaxial compressive stress in a concrete cube testing machine or similar device. Apply load axially at a uniform rate 14 N/mm2 per minute till failure occurs and note maximum load at failure.

CLAY- Generally, the presence of clay in moderate amount in a soil is desirable. Since clay has cohesive nature, it imparts plasticity to the soil when under moist condition. Thus the clay minerals act as natural binding agents for the cohesion less granular fraction of a soil (gravel, sand and silt). The soils which have

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CEMENT- cement can simply be described as being a mixture of lime and clay which is heated to about 1500c, and the resulting clinker has gypsum added and the sum is then ground to very fine powder. Optimum cement content for the stabilization is in the range of 5% to 10% where addition above 10% will affect the strength of the bricks in negative way. Opc is obtained by adding raw materials like calcareous materials and argillaceous materials. Ppc is obtained by adding pozzolonic materials like flyash, pumicites, volcanic ashes, shales, tuffs etc. in ppc waste utilization making it more environmental friendly. SOIL- soil is a product of nature. It possesses an inherently variable and complex charater. Not every soil is suitable for earth construction. Top soil and organic soil must not be used. Suitability of the soil depends on its constituents: sand, silt and clay proportions.

ATTERBERG LIMIT TEST- The atterberg limits are abasic measure of the nature of a fine grained soil. The atterberg limits can be used to distinguish between silt and clay. Liquid limit is the water content at which the soil has such a small shear strength that it flows to close a groove of standard width. PLASTIC LIMIT is the water content at which the soil begins to crumble when rolled into threads of specified size. SHRINKAGE LIMIT is the max water content at which a reduction in water content will not cause decrease in the volume of the soil mass. The PLASTICITY INDEX may be calculated as the difference of liquid limit and plastic limit. GRAIN SIZE ANALYSIS- a quantitative determination of the particle size distribution in a soil is made by sieve analysis and sedimentation analysis. HYDROMETER ANALYSIS-this method is used for the grain size analysis of the soil passing through 75 micron I.S. sieve out of the fraction passing 4.75mm I. S. sieve, to determine the percentage of various sized(silt and clay) particles. SPECIFIC GRAVITY- specific gravity of soil is the ratio of the weight of a given volume of soil particles in air to the weight of an equal volume of distilled water at a temperature of 4*c. COMPACTION TEST- the purpose of laboratory compaction test is to determine the proper amount of water at which the weight of soil grains in a unit volume of the compacted soil mass is maximum. The amount of water, thus calculated is called the “optimum moisture content”(OMC) and the corresponding density is called “maximum dry density”(MDD).

The process of manufacture of stabilized soil bricks involves the following five steps:

To find the strength of the stabilized soil bricks the soil samples have been mixed in various proportions. Table-3 shows the mix proportion with varying percentage of soil, clay and cement.

Table-4 shows the result of compressive strength of bricks at 7days. And Table-5 shows the result of compressive strength of bricks at 28days.figure-4 shows the graph between compressive strength of bricks at 28 days and cement content with varying proportions, and figure-5 shows the graph between compressive strength of brick at 7 days, 28 days and opc cement content with varying proportions and figure-6 shows the graph between compressive strength of bricks at 7 days,28 days and ppc cement with varying proportions.

• The bricks were unburnt and hydraulically pressed. The soil stabilized bricks was taken for strength determination after 7 and 28 days.

• The maximum strength of brick obtained was 3.873 N/mm2 at 98 KN load, stabilized soil bricks i.e. mixture of [ Ppc(10%)+clay(5%)+soil(85%) ].

• The minimum strength obtained was 0.632 N/mm2 at 16 KN load,stabilized soil brick i.e. mixture of[ Ppc(5%)+clay(5%)+soil(90%) ].

 Use of ppc as stabilizer in place of opc gives more strength to the bricks with the same proportions of soil and clay and stabilizer.

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• Use of opc cement at constant proportion of clay does not increase the strength of bricks produced by ppc cement at 28 days.

• The influence of stabilizer on compressive strength of bricks is shown in result. In this paper, a brief review on stabilized soil bricks is done.

• Stabilization of soil block using Portland pozzolana cement fulfills a number of objectives that are necessary to achieve a lasting structure from locally available soil. Some of those are: better mechanical characteristics (leading to better compressive strength), better cohesion between particles.

• Increase in cement content results in an increase in the compressive strength value of blocks made at the same constant compaction pressure.

• The result of this paper have revealed that compressed stabilized soil block can be used as an alternative wall making material.

• The amount of water content for the soil-cement mixture needs to be carefully controlled. there needs to be sufficient moisture for the cement to fully hydrate but no excess of water which would reduce the final density, increase porosity and reduce final strength.

• Previous researches showed that stabilized soil bricks demonstrate many advantages compare to conventional fired bricks. This stabilized bricks are environment friendly- no burning of bricks required. It is cost efficient. The utilization of earth in housing construction is one of the oldest and most common methods used by a larger percentage of the developing countries population.

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(28) Satprem maimi, production and use of compressed stabilized earth blocks, auroville earth institute, india,march2006. (29) David Edward Montgomery, bynamically-compactedcement stabilized soil blocks for low-cost walling, university of warwick, school of engineering, January 2002. (30) Craig, R.F, soil mechanics,E&FN spon, 1997. (31) African regional standards, compressed earth blocks standards, CDI andCRA terre-publication,1998. (32) Appropriate building materials for low cost housing African region, proceedings of a symposium held in Nairobi Kenya from 7 to 14 November 1983, E. & F.N. spon ltd, london1985. (33) Satprem Maini, modernity of earth architecture, presentation on national alternative building materials workshop Addis Ababa, Ethiopia, feb,2006. (34) F.O. Okafor, D.E. Ewa, the compressive strength of obudu earth blocks stabilized with cement kiln dust,july,2012. (35) Earth building materials and Techniques Select Bibliography, CRAT terre, aus der arbeit von gate,eschborn,1991. (36) Fitzmaurice, R., manual on stabilized soil construction for housing. Technical assistance program, united nations,1958. (37) American institute of architects. Environmental resource guide subscription. Washington: American institute of architects,1992. (38) Mchenry, Paul Graham, JR. Adobe and rammed earth buildings: design and construction. New York: john wiley, 1984.