ABSTRACT
High cost of cement has caused serious impact on housing delivery due to increase in energy costs and high demand which attracted many research interests in sourcing other alternatives cheaper materials. The use of rice husk powder in composites cement system was investigated. Paste of neat and blended Portland cement with 5%, 10%. 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, and 55% rice husk powder were cured in air under the same temperature and humidity condition. Compressive strength of the various mix proportions at 28 days were determined using standard compressive strengths testing machine. The hydration products of the high percentage replacement composite cement pastes were identified by x-ray diffraction analysis and compared with those made from 100% ordinary Portland cement pastes. Results indicate that only lower percentage replacement level such as 5% and10% rice husk powder contained the required amounts of silica which aided the hydration process producing samples with compressive strengths of 19.72N/mm2 and11.57N/mm2when compared with control sample with 33.33N/mm2. However, result of the x-ray diffraction analysis showed that the observed hydration products were mostly as expected due to the high replacement levels but the degree to which crystal phases were identified in one of the samples was unusual. The unusual behavior may be due to the fact that the calcium hydroxide initially formed was consumed during the curing period confirming the important pozzolanic reactions of the rice husk powder at such high replacement.