<p>Due to the local geology, expansive soils with weak geotechnical properties pose significant challenges to civil engineering projects. Enhancing soil strength and reducing plasticity are essential for supporting diverse construction endeavors. Given the abundance of lime and natural pozzolana in Algeria, this study investigates their influence on the geotechnical characteristics of clayey soils. The research examines the lime and natural pozzolana impact expansive clay soil's consistency, mechanical properties, classification, and microstructural and mineralogical composition. Soil samples are treated with lime and natural pozzolana at varying percentages (0% to 6% and 0% to 20%, respectively) and cured for 1 and 28 days to assess the effect of curing time. Results demonstrate that incorporating natural pozzolana significantly enhances the properties of lime-treated expansive soil, resulting in improved soil fabric and increased cementitious material production compared to lime alone. X-ray diffraction and microscopic analysis revealed the formation of new pozzolanic products (C-A-S-H) alongside existing C-S-H and C-A-H phases in lime-natural pozzolana-treated soil. The study effectively enhances clay soil's workability and geotechnical properties by combining lime and natural pozzolana, offering promising insights for soil improvement in civil engineering projects.</p>