Mitigation of Expansive Soil by Liquid Alkaline Activator Using Rice Husk Ash, Sugarcane Bagasse Ash for Highway Subgrade

Expansive soil has very low shear strength when wet and high swelling and high shrinkage characteristics. Due to this, it is one of the most problematic types of soil damaging buildings, roads, and pipelines each year throughout the world resulting in huge annual revenue loss. Due to the revenue losses the industrial waste used for amended the expansive soil. Rice husk ash and sugarcane bagasse ash are the industrial waste by-products from the rice mill and sugar mill respectively. This paper presents the behaviour of amended expansive soil with rice husk ash, sugarcane bagasse ash, and liquid alkaline activator stabilizer for highway subgrade. The liquid alkaline activator used is a mixture of sodium metasilicate (Na2SiO3.9H2O) and sodium hydroxide (NaOH) solutions of 1 M and 10 M concentration respectively. Strength and swelling characteristics of amended expansive soil were evaluated. Strength was determined by unconfined compressive strength and soaked California Bearing Ratio values. The swelling was determined by the expansion ratio and free swell index of the treated soil after 7, 14, and 28 days of curing. The strength of subgrade soil was observed to be increasing with the increase in rice husk ash and sugarcane bagasse ash content up to a certain limit and then decreases. The expansion ratios and free swell index were also observed to decrease while the increasing rice husk ash and sugarcane bagasse ash content and curing time increase with a fixed ratio of sodium metasilicate solution (Na2SiO3.9H2O) and sodium hydroxide (NaOH) (70:30) solutions.