Experimental investigation on stabilization of expansive subgrade soil using industrial waste (bagasse ash) and lime: a case of Koshe–Werabe road project, Central Ethiopia

This paper presents the results of an experimental study undertaken to investigate the effects of using industrial waste bagasse ash with lime for improving the strength and mechanical properties of expansive subgrade soil. Preliminary analysis of the natural soil revealed that it is black, highly plastic, and classified as A-7-5 according to the AASHTO soil classification system and CH in the USCS system. Geotechnical laboratory tests such as specific gravity, Atterberg limits, swelling properties, compaction, and CBR were performed to assess the properties of the stabilized soil. The soil was stabilized with bagasse ash at different concentrations of 4, 8, 12, and 16%, in combination with 4% lime, based on the dry weight of the soil. All stabilized soil samples were cured for 7 days before testing for Atterberg limits, compaction, and CBR. The experimental results showed that stabilization with bagasse ash decreased the specific gravity, liquid limit, plasticity index, swelling, and maximum dry density (MDD), while increasing the optimum moisture content (OMC) and CBR and curing had little to no effect. Similarly, the combination of lime and bagasse ash stabilization resulted in decreased specific gravity, liquid limit, plasticity index, swelling, and MDD, while increasing OMC and CBR and curing had a significant effect. Overall, the findings of this study suggest that treating expansive soil with a combination of bagasse ash and lime leads to more significant improvements in geotechnical properties compared to using bagasse ash alone.