The geotechnical behaviour and microstructural characteristics of the alkaline residue/cement-stabilized expansive soil under wetting–drying cycles

In order to explore the geotechnical behaviour of expansive soil stabilized by alkaline residue/cement (ARC) under wetting–drying (W–D) cycles, the shrink–swell characteristics, unconfined compressive strength (UCS), compressibility and microstructural characteristics are experimentally investigated in this study. The findings indicate that the incorporation of ARC, particularly with an alkaline residue (AR) content of less than 5%, significantly mitigates the shrink–swell behaviour, reduces soil compressibility and enhances the UCS of the soil. Beyond this threshold, the soil's strength decreases and compressibility increases with increasing W–D cycles. Microstructural analysis reveals the formation of beneficial cementitious products such as calcium aluminate hydrate (C-A-H), calcium silicate hydrate (C-S-H) and ettringite (AFt) that contribute to improving the engineering performance in the early stages of the W–D cycles. Nevertheless, as the W–D cycles continue, these beneficial products diminish, leading to an increase in soil cracks and pores, which indicates a degradation in soil performance. The research posits that ARC can effectively serve as a partial substitute for cement in the stabilization of expansive soils, with the amount of AR within 5%. Despite ARC's environmental advantages as an alternative binder, it may encompass harmful elements. Therefore, a comprehensive environmental risk assessment is essential. Further studies are needed to discern the enduring effects of environmental variables on soils stabilized with ARC.