<p>This study evaluates the cyclic wet-dry durability behaviour of expansive soil stabilized with lime-activated bagasse ash (BA). BA was incorporated into the soil at proportions of 0–18% at 3% intervals by dry weight, followed by the addition of lime at 0–6% at 2% intervals to the optimum BA content to identify the most effective stabilizer combination. The treated soil mixtures were examined through index properties, compaction characteristics, swelling behaviour, unconfined compressive strength (UCS), and California bearing ratio (CBR) tests. UCS specimens were cured for 0, 7, 14, and 28 days, while soaked CBR tests were conducted after 4 days of immersion. The results depicted that the combination of 15% BA and 4% lime provided the optimum performance, resulting in notable strength improvement and reduction in swelling potential compared with untreated soil. Durability assessment was performed on specimens cured for 0 and 28 days by subjecting them to four wet-dry cycles, which caused progressive reductions in strength and specimen mass. Microstructural observations confirmed the development of cementitious reaction products in the treated soil, while the development of pores and cracks after cyclic exposure explained the degradation in mechanical behaviour. The findings demonstrate that lime-activated bagasse ash can improve the performance of expansive soils under cyclic moisture conditions, although strength loss under repeated wet-dry exposure should be considered in practical applications.</p>