Modified water-cement ratio law for compressive strength of rice husk ash concrete

Abstract

This work examines the modification of age long water-cement ratio law of Ordinary Portland Cement (OPC) concrete to cater for concrete with Rice Husk Ash (RHA). Chemical analysis of RHA produced under controlled temperature of 6000C was carried out. A total of one hundred and fifty (150) RHA concrete cubes at five different water/binder ratios and six replacement levels of RHA (s%, 10%, 15%, 20%, 25%, 30%) were produced with specific attention given to water/cement (w/c) content and RHA/water (r/w) content. The cubes were subjected to compressive strength test at 56 days of curing producing a compressive strength in the range of 3.77 N/〖mm〗^2 and 34.04 N/〖mm〗^2. A linear polynomial model was fitted into the experimental data using Minitab Package and was found adequate with an adjusted coefficient of determination of 73.0%. Test results show that the compressive strength of hardened RHA concrete depends on cement/water content by weight on one part and RHA/water content by weight on the other part. This indicates that the model equation is suitable to evaluate the compressive strength of RHA concrete at 95% confidence interval and the linear model has the capability of explaining the variability in the data by 73%.