Geotechnical Behaviour and Utilisation of Sustainable Waste with Expensive Soil in Rural Roads as Subgrade Material

A common effective technique used in stabilising expansive soils is using different sustainable materials and lime. The prospects of using bottom ash and lime as subgrade materials to enhance the geotechnical properties of clayey soil are discussed in the present paper. Laboratory tests including cost analysis have been conducted on various combinations and ratios of clayey soil (S), bottom ash (BA), and lime (L). The test results show that the inclusion of 15% BA into clayey soil resulted in lower liquid limits and plasticity indices. The maximum dry unit (MDU) weight has been found to reduce when BA was added to clayey soil. When 6% lime was added to the S:BA (79:15) mixture, the MDU weight increased even further. The S:BA:L combination in the ratio of 79:15:6 exhibited the highest California bearing ratio (CBR) value of 11.2%. The combination of S, BA (15%), and L (6%) has been considered to have optimal properties. The overall pavement thickness using S:BA:L combination for 15-year design life was reduced by about 37% as compared to clayey soil alone. A cost reduction of nearly 24% was noted when using the S:BA:L combinations compared to using clayey soil subgrade alone. The significant savings highlight the economic benefits and long-term viability of the S:BA:L paving material mix. Therefore, the major objective of the present paper was to study the effect of bottom ash and lime on the physical, compaction characteristics, and subgrade strength of clayey soil and bulk utilization as subgrade material to avoid the negative effects of waste on the environment and minimize the demand for natural resources like aggregates and sand.