Investigation of the effects of Rice Husk Ash (RHA) on the engineering properties of red coffee soil for sub - grade

Abstract

Traditionally, rice husk has been considered a waste material and has generally been disposed off by damping or burning, although some has been used as low grade fuel. However, when burned, th e resulting Rice Husk Ash (RHA) is a pozzolanic material that c ould be potentially used in stabilization of clayey soils for road construction. This study investigates the effects of RHA on the engineering properties of one of the co mmon road construction material in Kenya, the red coffee soil. The investigation includes laboratory tests and analysis of the results of the tested samples. The properties that were evaluated includes the California Bearing Ratio (CBR), plasticity index (PI), and linear shrink age with Rice Husk Ash content of 3%, 5%, 7%, 9% and 11% by weight of the dry soil. From analyzing the laboratory results, it was found that addition of RHA to the natural soil generally reduced the liquid limit and the linear shrinkage, with a maximum re duction of 13% and 44% respectively after treatment with RHA content of 11%. In addition, the soaked CBR and plastic limit increased by approximately 500% and 31% respectively after addition of 11% RHA. It was also found that the plasticity index of the st abilized red coffee soil also reduced by 48% after treatment with 11% Rice Husk Ash .