Structural Characteristics Of Soilcrete Blocks

ABSTRACT 

This work investigates the structural characteristics of soilcrete blocks (lateritecement blocks and laterite-sand-cement blocks) produced with locally available and affordable laterite. Scheffe’s simplex method and Osadebe’s regression theory were used to formulate mathematical models for optimisation of properties of soilcrete blocks which include compressive strength, split tensile strength, shear strength, flexural strength, Poisson’s ratio, modulus of elasticity, shear modulus/modulus of rigidity and water absorption for the two types of soilcrete blocks. At the end of the day, eight (8) models were formulated for the eight characteristics based on Scheffe’s method, eight (8) models based on Osadebe’s method for each type of block. These made it a total of thirty-two (32) models. Consequently, thirty two (32) computer programs were written using basic language. Statistical tools were used to verify the adequacy of the models. With the aid of the computer, the models will be able to predict the mix proportions that will give the desired property. The models can also give the desired property if the mix ratios are specified. The overall result in the use of the models will lead to time, energy and cost savings in the production of soilcrete blocks. The maximum compressive strength predictable by Scheffe’s model is 3.01N/mm2 for sand-laterite blocks and 2.148N/mm2 for soilcrete blocks. The maximum flexural strength obtainable from Scheffe’s model is 1.718N/mm2 for sandlaterite blocks and 1.452N/mm2 for soilcrete blocks. The maximum split tensile strength predictable by Scheffe’s model is 1.45N/mm2 for sand-laterite blocks and 0.88N/mm2 for soilcrete blocks. The maximum Poisson’s ratio obtainable from Scheffe’s model is 0.112 for sand-laterite blocks and 0.174 for soilcrete blocks. The maximum static modulus of elasticity predictable by Scheffe’s model is 6.414GPa for sand-laterite blocks and 5.149GPa for soilcrete blocks. The maximum shear modulus/modulus of rigidity obtainable from Scheffe’s model is 2.885GPa for sandlaterite blocks and 2.195GPa for soilcrete blocks. The maximum shear strength predictable by Scheffe’s model is 0.43N/mm2 for sand-laterite blocks and 0.363N/mm2 for soilcrete blocks. The maximum water absorption predictable by Scheffe’s model is 7.29% for sand-laterite blocks and 6.16% for soilcrete blocks.  The percentage difference between Scheffe’s model result and Osadebe’s model result (for compressive strength of sand-laterite blocks) ranges from a minimum of 0.25% to a maximum of 6.66% which is insignificant. From the laboratory cost analysis, the percentage cost savings in using soilcrete block is 46.67% while that of sand-laterite blocks is 42.1% which is very significant.