Expansive soils challenge the stability of several civil engineering structures. Because of the presence of Montmorillonite clay mineral, they have the inherent property of swelling and shrinking upon wetting and drying. Researchers proposed several ground improvement and foundation techniques to enchase the properties of these soils. Cushion materials, particularly Cohesive Non– Swelling (CNS) cushions, attracted the attention of civil engineers due to their simplicity and long-term stability. To avoid the problem of the non-availability of required soil, a technique is presented in this study to convert local expansive soils into suitable CNS materials via chemical stabilisation. The study uses clayey sand from the Tirupati region of Andhra Pradesh. Admixtures such as fly ash and lime chemically modify native soils into CNS materials. The effectiveness of these prepared CNS materials in reducing expansive soil heave is investigated using model test tanks. SEM and XRD analyses are also used to determine changes in soil microstructure. According to the findings, 5% lime and 20% fly ash are optimal for preparing CNS material. The microstructure of the stabilised soil revealed the formation of cementation compounds, which improved the strength of the native soil stabilization using fly ash.