VALORIZATION OF WASTE GLASS POWDER AS AN ALKALI-ACTIVATED STABILIZER FOR EXPANSIVE SOILS

Expansive soils, which cover nearly 20% of the global land area, exhibit severe swelling–shrinkage, low strength, and rapid deterioration under cyclic moisture variations. Conventional soil stabilizers such as cement and lime mitigate these deficiencies but at the expense of significant carbon emissions, releasing approximately 0.9 tons of CO2 per ton of binder produced. Simultaneously, municipal solid waste continues to accumulate, with glass waste forming a major non-biodegradable fraction that predominantly ends up in landfills. Addressing these dual challenges, this study evaluates alkali-activated waste glass powder (WGP) as a sustainable stabilizer for expansive soils. A synthetic expansive soil was treated with WGP up to 50% replacement and activated using 5M NaOH under normal curing. Unconfined compressive strength (UCS) testing revealed substantial improvement, with 28-day strength increasing from 69 kPa in untreated soil to 2152 kPa at 50% WGP replacement, representing nearly a 30-fold enhancement. Complementary X-ray diffraction (XRD) and scanning electron microscopy (SEM) verified the formation of aluminosilicate gels and matrix densification, which corroborated the observed strength enhancement. The findings establish alkali-activated WGP as a sustainable alternative to conventional soil stabilizers, simultaneously improving expansive soil performance and diverting glass waste from landfills.