INVESTIGATING THE EFFECTIVENESS OF RICE HUSK ASH AS STABILIZING AGENT OF EXPANSIVE SOIL

Abstract

Expansive soils pose a significant threat to structures due to its ability to cause damage from the footing up to the superstructure. This paper intends to provide an economic and environment-friendly method of mitigating the swelling potential of expansive soil by replacing a set volume of expansive soil with rice husk ash (RHA) – an abundant waste material produced by the biomass power plant. The swelling behavior of the soil mixtures was analyzed through its expansion index obtained via ASTM D4829.  Results of the tests revealed that the mixture containing 20% and 25%  RHA are considered non-expansive soil.  Soil stability parameters were also obtained through the tests specified by ASTM D4609.The tests on the soil stability parameters revealed that soil-RHA mixtures exhibited an improvement in the Atterberg limits which garnered a 36.32% decrease in the liquid limit and 64.75% decrease in the plasticity index; however, a decline was observed in the compaction characteristics and the unconfined compressive strength.  Soil-RHA mixtures experienced a maximum decrease of 230 kg/m³ in the maximum dry density and a 40.17% increase in the optimum moisture content. The unconfined compressive strength of treated soils yielded a decrease of as much as 194.2 kPa as well as a decrease in the cohesion development of the soil. The results revealed that while an increase of the RHA content reduces the swelling potential of soil, other strength parameters such as the compaction behavior and the unconfined compressive strength of the soil declines.