Effect of rice husk ash on the swelling pressure of bentonite soil stabilized with lime in the presence or lack of sulfate

Lime is an effective substance to decrease the swelling of expansive soils. The effective use of lime as a stabilizing agent in the presence of sulfate under some circumstances has been questioned due to the formation of ettringite. In this research, the effect of the addition of rice husk ash (RHA) on the swelling pressure of a bentonite soil (B) modified with lime (L) and calcium sulfate or gypsum (G) was investigated. Nine groups of twin compacted samples, namely, bentonite soil (B), B + L (3% by dry weight), B+3%L+ 5%G, B+3%L+RHA (5, 10 and 15% by dry weight, respectively) and B+3%L+5%G+RHA (5,10 and 15%, respectively), were prepared and tested immediately for 1D constant volume swelling pressure measurements. Similar groups of samples were prepared and tested after 7 and 28 days of curing. The results indicated the effect of RHA in decreasing the magnitude of swelling pressure in comparison with untreated and treated soil without RHA