Stabilization of Expansive Subgrade Soil with Cow Dung Ash and Lime

Abstract

This paper presents the investigation made on cow dung ash (CDA) alone and a combination of CDA and lime for stabilizing expansive  black clay soil with high plasticity used as a subgrade for road pavement. The study was mainly conducted to assess the performance of  expansive black clay soil when stabilized with CDA and lime, and its suitability to solve the issue of structural damage identified on the  road. The chemical compositions of lime, CDA, and natural unstabilized subgrade soil (control) were determined using X-ray fluorescence.  The plastic limit (PL), plasticity index (PI), liquid limit (LL), linear shrinkage (LS), maximum dry density (MDD), optimum  moisture content (OMC), free swell index (FSI), California bearing ratio (CBR) and unconfined compressive strength (UCS) of the control  soil, the control soil mixed with varying quantities (0%, 6%, 10%, 14%, 20%, and 25% by dry weight of the soil) of CDA, and the control soil  mixed with varying CDA-lime combinations consisting of mixtures of 5% lime with 10%,15% and 20% of CDA were determined  experimentally. The experimental outcomes showed that the soil stabilized with the CDA-lime combination is synergistic, improves the  CBR and UCS and lowers the PI, and swelling potential of the soil more than the soil stabilization with CDA alone.