MODELLING COMPRESSIVE AND FLEXURAL STRENGTHS OF CONCRETE WITH PERIWINKLE SHELLS AS PARTIAL REPLACEMENT OF COARSE AGGREGATES BY RESPONSE SURFACE METHODOLOGY

Abstract

Concrete has been identified over many decades as the most common and used material in the construction industry. The continuous use of normal concrete products has resulted into high cost of constituent materials, high self weight, and depletion of rock fragments, which distorts the ecosystem. This research work focuses on the compressive and flexural strength of concrete using periwinkle shell as partial replacement to coarse aggregate. The physical and mechanical properties of sharp sand, granite and periwinkle shell were determined. Absolute volume method of mix design was used with the inclusion of four independent variables of water/cement ratio, total aggregate/cement ratio, coarse aggregate/total aggregate ratio and periwinkle shell/coarse aggregate ratio, and the MINITAB software was used to generate the number of mixes for the work. A total of 204 each of concrete cubes of 150mm x 150mm x 150mm and concrete beams of 100mm x 100mm x 500mm were cast from the generated mixes, tested, and their physical and mechanical properties were determined. The analyses of the result were done and computations of compressive and flexural strengths were calculated. The results obtained for the 28th day compressive and flexural strengths ranged from 9.99-19.30, and 6.25-11.13 N/mm2 respectively. As obtained from experiment, the results from the mechanical properties test complied with the requirement of structural and non structural lightweight concrete as stipulated in British Standard, BS 8110 :Part 2 :1985. Concrete mixes which gave compressive strengths greater than 17N/mm2 can be used as structural lightweight concrete. The polynomial models have proven to be adequate in predicting the compressive and flexural strength of concrete incorporating periwinkle shell to 80.11% accuracy at the minimum.