OPTIMIZATION OF COMPRESSIVE STRENGTH OF PERIWINKLE SHELL CONCRETE USING SCHEFFE’S MODEL

Abstract

This study investigates the application of scheffe’s model in compressive strength optimization of periwinkle shell-coarse aggregate (PSCA) concrete. Physical properties of the aggregates such as specific gravity, bulk density, sieve analysis and workability of concrete were determined. Specific gravities of fine and coarse aggregates were 2.62 and 2.68 respectively, Moisture content for aggregate for fine and coarse aggregate were 7.08 and 3.03 respectively. The bulk densities were 1612.82kg/m3 and 1394.64kg/m3 respectively. From the sieve analysis test, the sand belonged to zone 2 and well graded with coefficient of gradation of 1.04. Ninety 150mm x150mm x 150mm cube specimens were produced for the compressive strength test. Model was fitted to data obtained on the compressive strength and mathematical model was developed based on Scheffe’s model. The formulated model was tested for adequacy at 95% level of confidence using t-statistic. The compressive strength of concrete was observed to decrease with increase in the percentage replacement of periwinkle shells (PS). The reduced value of the compressive strength may be due to lower specific gravity, water absorption capacity value of periwinkle shell compared to that of crushed granite. The blending of the two materials caused a reduction in strength value of the end product since specific gravity is strength related. The reduced compressive strength value may also be due to the fact that periwinkle shell has fewer binding properties compared to crushed granite. After 28 days of water curing, the concrete gave an average optimum compressive strength value of 25.78N/mm2 corresponding to a mix proportion of 1, 0.1, 1, 1.9 (cement, periwinkle shell, sand, granite) at a water-cement ratio of 0.4. This compressive strength value obtained at 5% replacement is within the recommended value required for plain concrete works, lean concrete, simple foundations, masonry walls and other simple construction works in low- cost housing constructions