Variation of Strength of OPC-Rice Husk Ash Cement Composites with Water

This work investigated the variation of strength of OPC-RHA cement composites with water-cement ratio. 180 concrete cubes of 150mm x 150mm x 150mmwere produced with OPC and RHA using a constant mix ratio of 1:2:4, percentage OPC replacement with RHA of 0%, 5%, 10%, and 15%, and six water/cement ratios of 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9.180 sandcrete cubes and 180 soilcrete cubes were also produced. Three concrete, sandcrete, and soilcretecubes for each percentage OPC replacement with RHA and water/cement ratio were crushed to obtain their compressive strengths at 28 and 50 days of curing. It was found that the strength values of control composites generally reduced with increase in water-cement ratio, with maximum 28-day strength values of 24.00N/mm2 for concrete, 9.80N/mm2 for sandcrete, and 8.80N/mm2 for soilcrete obtained at water-cement ratio of about 0.4. On the other hand, the strength of OPC-RHA composites varied with both percentage replacement of OPC with RHA and water-cement ratio. Maximum 28-day strength values of 22.50N/mm2 for concrete, 9.10N/mm2 for sandcrete, and 8.10N/mm2 for soilcrete at 10% replacement of OPC with RHA were obtained using water-cement ratio of about 0.6 while maximum strength values of 20.30N/mm2 for concrete, 8.30N/mm2 for sandcrete, and 7.40N/mm2 for soilcreteat 20% replacement of OPC with RHA were obtained at water-cement ratio of about 0.7. Thus