AbstractThis paper presents technical and sustainability analyses evaluating the feasibility of using recycled plastics in the stabilization of kaolinite rich soils. A series of experimental studies were performed to evaluate the stress-strain behavior of soil–cement mixtures reinforced with recycled high-density polyethylene (HDPE) and polypropylene (PP) plastic pellets. Laboratory studies were performed on soil samples containing different percentages of cement, recycled HDPE, and PP pellets to investigate the effectiveness of recycled plastics in enhancing the strength characteristics and ductile behavior of kaolinite soils. The results indicated that soils stabilized with 9% to 15% by weight of cement and reinforced with 4% to 12% by weight of recycled HDPE and PP pellets (sized 3 to 4 mm) met the strength requirements for pavement base and subgrade layers. It was also observed that the plastic-reinforced soils showed a ductile nature with increased failure strain values. Cumulative sustainability index (Isus) was defined and was used to evaluate the environmental impact of using recycled plastics in pavement base and subgrade layers. The treatment mix design with the lowest Isus value is recommended for future implementation projects. This research highlighted the use of recycled HDPE and PP pellets in enhancing the strength and deformation characteristics of pavement base and subgrade layers.