Author : Dr. Shiren Osman Ahmed

Rice husk ash (RHA) is an agricultural waste product which is a pozzolanic material. It is blended with the cement for manufacturing concrete. It reduces the environmental impact of the cement industry. Blending of cement with supplementary cementitious materials like fly ash and rice husk ash makes concrete more durable. This paper studies effect of a partial replacement of cement with various ratios of rice husk ash (RHA) on physical and mechanical properties of concrete. Three mixtures were prepared with proportions of 4, 8, and 16% RHA by weight of cement in addition to 15% fly ash (FA) by weight of cement to be compared with a reference mixture with 100% Portland cement. Compressive strength test, tensile strength test, flexural strength test and rate of water absorption test were performed at different ages of curing. Test results have reflected that the compressive strength, tensile strength and flexural strength achieved with 16% replacement of cement with RHA maximum increase. Compressive strength increased with 16% RHA by 12.5% at 56 days age compared to compressive strength of control mix. Flexural strength increased with 16% RHA by 17.33% at 56 days age compared to flexural strength of control mix. There is significant development in mechanical properties compared to control mix. The mixture with 16% RHA showed the lowest ratios of water absorption by about 2.8% and 2% at 28 and 56 days of cuing, respectively.

Keywords: High strength concrete, Rice husk ash, Compressive strength, Fly ash, Rate of water absorption