<p>Expansive soils exhibit significant volume changes due to moisture variations, necessitating soil stabilization. Conventional stabilizers, such as lime and cement, have environmental drawbacks due to their carbon emissions. In this study, wollastonite powder (WP), a natural silicate mineral, and polyester fiber (PF), a synthetic reinforcing material, were used to improve the strength properties of expansive soil. Experimental investigations were conducted on the collected soil samples with varying percentages of WP (0-12%) and PF (0.15-1%) were added at the optimum WP content of 6%. Laboratory tests were conducted according to Indian standards, such as Atterberg limits, compaction tests, and unconfined compressive strength (UCS) tests at curing days of 0, 7, and 14. The results indicated that adding WP significantly reduced the liquid limit and plasticity index while increasing the plastic limit of the soil. The maximum dry density decreased, and the optimum moisture content increased with the addition of WP. The UCS of soil with an optimum 6% WP increased four times compared to untreated soil with 14 days of curing. The incorporation of 0.5% PF with soil and 6% WP exhibited the highest improvement in UCS, 5-times more than that of untreated soil, after 14 days of curing. Cementation compounds were observed from scanning electron microscopy and X-ray diffraction. The combined use of WP and PF is an effective and eco-friendly method for improving the mechanical properties of expansive soil. A comparative CO₂ assessment indicates that wollastonite stabilization has a lower carbon footprint than lime and cement stabilization within the material-production system boundary.</p>