The paper assesses the use of rice husk ash (RHA) as an admixture in concrete in normal environment by determining the effect of addition of RHA of 0%, 5%, 10% and 15% respectively to concrete grades 20 and 30 concrete respectively. RHA used was obtained by burning rice husk obtained from a local mill in Kano. The husk obtained was sun dried, screened and burned at a temperature of 400oC in an incinerator. The ash obtained was cooled and sieved through a 425μm sieve and added as an admixture during mixing. A concrete mix design in accordance with Department of Environment (DOE), U.K (1975) method as reported by Teychem et al (1975) was adopted to proportion the constituents of both grades of RHA Concrete. Concrete mixes of both grades of concrete were prepared and the properties of fresh and hardened concrete assessed. The compressive strength of cubes of samples of RHA concrete cured in water were determined at 7, 28 and 56 days respectively in accordance with BS 1881 part 116 (1983). The results showed that the slump of RHA concrete increases with increase in percentage addition of RHA for both concrete grades. The compressive strength of samples of both concrete grades cured in water increases with addition of 5% and 10% RHA respectively but 5% addition of RHA had a better improvement in strength. Further increase in addition of RHA (15%) decreased the strength of RHA concrete.
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