Some engineering properties of sandcrete blocks containing rice husk ash

Abstract

The high and increasing cost of cement, coupled with its continuing scarcity has contributed to the non-realization of adequate housing for both urban and rural dwellers in Nigeria. As such any material that could complement cement but was much cheaper would be of interest. Rice husk ash has been found to possess some pozzolanic properties. If found adequate for partially replacing cement in sandcrete blocks, it would drastically reduce the cost of building in Nigeria, since sandcrete blocks are the major cost component of the most common building forms in the country. The rice husk ash (RHA) used was found to have a specific gravity of 1.54 and its chemical constituents met the BS 3892 and ASTM C-618 requirements for pozzolanas. Addition of the RHA in cement paste increased both the initial and final setting times. For a given hydration period and mix proportions, the strength of the blocks decreased with increasing RHA content. Sandcrete mix of 1:6 (cement/sand) ratio with up to 40%, cement replacementwith RHA and 1:8 ratio with cement replacement of up to 30% with RHA, are adequate for sandcrete block productions for both urban and rural dwelling in Nigeria.