Effect of Nigerian Rice Husk Ash on Some Engineering Properties of Sandcrete Blocks and Concrete

Sandcrete blocks have been in use in many nations of the world including Nigeria for a long time, playing a major role in the building and construction industry. In the investigation described in this study rice husk ash (RHA) has been used to partially replace cement in both concrete and sandcrete block manufacture. RHA having pozzolanic properties would reduce the demand of Portland cement whose cost has soared at the moment in Nigeria and hopefully help reduce the unit cost of both concrete and sandcrete block. Results suggested that the addition of RHA in the mix produced sandcretes of lower density, meaning that the density of the blocks actually decreased as the RHA content in the mix increased. In addition it was observed the compressive strength of the sandcrete blocks was not enhanced by the use of RHA. It was also observed that10% RHA content in the sand-cement mix is the optimum for improved structural performance. RHA however had a fairly significant effect on the compressive strength of the concrete cube specimens increasing the latter by nearly 17% (at 28 days) and at 5% RHA content. Concrete made with 20% RHA content is suitable for low-cost housing development.