Sustainable Stabilization of Expansive Clays with Waste Glass and Polymer for Improved Pavement Subgrades

Expansive clays present significant geotechnical challenges, often damaging structures and road networks, and requiring reliable stabilization techniques. This study investigates the combined use of waste glass and vinyl acetate ethylene (VAE) polymer to stabilize two types of expansive clays (i.e., slightly and highly expansive), offering a potential solution that addresses both environmental and engineering concerns. Fixed glass contents of 10% and 15% were introduced to the highly expansive and slightly expansive clay, respectively, alongside varying polymer contents of 0, 1, 1.5, and 2%. The stabilized clays were subsequently evaluated through a comprehensive series of physicochemical, microstructural, and mechanical tests, including X-ray microCT, X-ray diffraction, X-ray fluorescence, thermogravimetric analysis, standard compaction, unconfined compression strength (UCS), California bearing ratio (CBR), resilient modulus, swelling-shrinkage testing, and soil-water retention curve. The results revealed that treatment with waste glass and an optimum polymer dosage of 1.5% significantly enhanced the UCS, CBR, and resilient modulus for highly expansive clay, increasing from 1.18 to 1.75 MPa, 20% to 31.7%, and 156.05 to 232.91 MPa, respectively. Similarly, for slightly expansive clay, UCS increased from 1.10 to 1.31 MPa, CBR from 18.9% to 30.20%, and resilient modulus from 175.66 to 236.92 MPa. A reduction in the mechanical strength was observed upon increasing the polymer content beyond 1.5%, although a polymer dosage of 2% proved most effective in mitigating swell-shrink behavior.