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Effect of Partial Replacement of Ordinary Portland Cement (OPC) with Ghanaian Rice Husk Ash (RHA) on the Compressive Strength of Concrete

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Document pages: 11 pages

Abstract: Thecost of cement has made concrete production expensive such that the housingdeficit in developing countries is on the rise despite all the efforts bygovernments and other stakeholders to produce affordable housing units for thepopulace. Ashes of agricultural products such as rice husk, known as mineraladmixtures may have pozzolanic characteristics which would be more beneficialto the housing industry in terms of strength gain and economy than beingpollutants to the environment. Rice Husk Ash (RHA), because of its finelydivided form and very high silica content and amorphousness, proved to beuseful for strength gain of Rice Husk Ash Concrete (RHAC). Rice husk ash wasmanufactured by uncontrolled burning, ground, sieved and replaced with cement at0 , 5 , 10 , 15 , 20 and 25 in mass for the mixes C20, C25, C30 and C35 wheretheir compressive strengths were verified at 3, 7, 14, 21, 28, 56, 90 and 180days. The X-ray diffraction pattern list indicated amorphous as well asdiffused peak of about 8000 counts of SiO2 representing crystallinestructures identified as cristobalite. A physical examination of the RHA showedvery fine appearance, grey color and specific gravity of 2.06. The chemicalanalysis also revealed the existence of oxide content to be 55.8 representing0.78 of Fe2O3, 54 of SiO2 and 1.06 of Al2O3 representing 20.23 lower than the minimum value of 70 required for pozzolans.Generally, the compressive strength values decreased as the RHA content in themixes increased but when compared to the control concrete the optimumreplacement percentage of Ordinary Portland Cement (OPC) with RHA at 5 showedan increase above the control concrete for C20 mix. The increase in the RHA inthe mixes resulted in the high demand for water in all the mixes.

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