Application of Response Surface Methodology in Predicting and optimizing the properties of Concrete containing Ground Scoria and Metakaolin blended Cement in Concrete

Abstract

The effect of Metakaolin and ground Scoria on various properties of concrete were investigated and optimised using Response Surfaces Methodology (RSM) in this study. Seven batches of concretes were cast at water to cement ratio of 0.5 and 5% fixed Metakaolin with 0, 5, 10, 15 and 20% Ground Scoria replaced cement. The resulting concrete then was tested for Slump. The Concrete cubes were cast and cured for 3, 7, 14, 28 and 60days before Water absorption and Compressive strength test were carried out. at all replacement levels of Metakaolin/Scoria content, Workability, Water absorption, Density and Compressive strength decreased when compared with the control concrete. However, Water absorption, Density and Compressive strength slightly increased with increase in curing age. The models developed were quite accurate as the percentages of error were in a good agreement and can explain the variability in Metakaolin/Ground Scoria concrete. Numerical method of optimisation was applied to determine the optimum mix proportions for Metakaolin/Ground Scoria. The optimum mix of concrete was obtained by addition of 8.60% GS after curing for 12-days with 0.8 desirability. Based on the result of optimisation, incorporating the optimum values of 13.6% (5%MK+8.6%GS) metakaolin and ground Scoria in concrete as cement substitute for every one kilogram of cement, can potentially result in reduction of CO2 emissions by 0.07-0.1224kg.