Effect of percentage replacement of cement with rice husk ash on the compressive strength of 56_aged concrete.

Abstract

This study investigates the effect of Rice Husk Ash (RHA) used in several proportions as partial replacement for cement on the concrete beyond normal curing age of 28 days. The RHA used in this study has a chemical composition of SiO2 (63.28 %), Al2O3 (1.88 %) and Fe2O3 (0.54 %). Twelve (12) concrete cubes were cast for each 0, 5, 10, 15, 20, 25 and 30 % replacements by weight of RHA for OPC, in the proportion of 1:2:4 concrete mix and 0.5 water/cement ratio to achieve a total of eighty four (84) cubes. The cubes were cured and tested for the compressive strength at age 7, 28 and 56 days. It is observed that the use of RHA may reduce the compressive strength of concrete at an early age, but enhanced the strength from 28 days and beyond. A maximum compressive strength of 19.11 N/mm2 at 56 days is higher than that obtained for the control (13.16 N/mm2) at 28 days. A maximum of ten percent (10 %) RHA replacement of OPC is recommended in the production of lightweight concrete.