Multiscale analysis of traditional and non-traditional additive amended expansive soil-A comparative evaluation

Abstract

The expansive soils have always been complex and problematic for construction purposes and challenging for the geotechnical fraternity. However, structural alterations and chemical stabilization methods have been practiced successfully in many practical applications. These soils interact with the chemical additives based on the chemical composition, curing period and quantity. The stabilization methods have also focused on non-traditional, eco-friendly additives, which can be a suitable alternative to conventional alkaline additives. However, extensive experimentation is required at various testing levels to understand the stabilization mechanism and the longevity of the additives in the soil medium. The present study uses lime, a conventional additive and a non-traditional additive-lignosulphonate (LS), to stabilize the expansive soil. The interaction mechanism of soil and the additives is investigated at macroscale and microscale levels to understand the modifications rendered to the virgin soil. The effect of the additives in terms of quantity and curing period is studied with respect to plasticity characteristics, strength development and microstructural modifications. The interaction behaviour of soil and the additive is compared at each level, and a probable interaction mechanism is proposed for both additives from this study. The criticality of lime amendment depends on the curing effect and the quantity. A strength improvement factor of 9 and 2 is observed for lime and LS amendment. The compressive/tensile strength ratio is higher for lime amendment, indicating excessive brittleness compared to LS. The conventional additives contribute to higher strength and brittleness, as opposed to lower strength gain and less brittleness of non-conventional additives.