Effect of Fly Ash and Rice Husk Ash on Index and Engineering Properties of Expansive Clays

Many innovative ameliorating techniques including chemical stabilization have been in practice for improving the behaviour of problematic, highly expansive clays. This paper presents a comparative study on the effect of fly ash (FA) and rice husk ash (RHA) on index and engineering properties of an expansive clay. Liquid limit (LL), plastic limit, plasticity index (PI) and free swell index (FSI), and coefficient of permeability (k), unconfined compressive strength and swelling pressure were determined at varying quantities of FA and RHA. Coefficient of permeability, swelling pressure and unconfined compressive strength of the FA-clay and the RHA-clay blends were determined at their respective OMC and MDD obtained from Proctor compaction tests. LL, PI and FSI decreased significantly with increasing FA and RHA contents. Coefficient of permeability, however, increased with additive content. Further, swelling pressure of the blends decreased with increasing additive content.