Extensive subgrade foundations in the form of BC clay soils in central and peninsular India have been the cause of recurring geotechnical problems because of their cyclic swelling-shrinkage behavior. This study is a laboratory-based investigation involving the chemical treatment of expansive clays via a novel polymer treatment process that uses liquid Polyvinyl Acetate (PVA) emulsion. Untreated and treated clay layers have been evaluated based on the results of Atterberg index tests, light compaction tests, Unconfined Compressive Strength (UCS), and soaked California Bearing Ratio (CBR) profiles at varying additive concentrations (0.5%, 1.0%, 1.5%, and 2.0% in relation to the dry weight of soil). The chemical cross-linking process results in the formation of macromolecular envelope barriers that encapsulate the expansive montmorillonite layer structure, thereby limiting their water-holding capacity and interstitial pathways. Optimum polymer treatment at 1.5% has led to more than 115% increases in UCS values and improved subgrade bearing capacity.