Reinforcing Weak Soils: A Sustainable Approach Using Shredded Plastic Waste

Plastic waste has become a global environmental threat due to the increase of its accumulation, necessitating for sustainable waste management strategies to alleviate ecological harm. At the same time, many engineering projects face challenges due to the presence of weak soils, underscoring a need for soil improvement techniques. To cope with the challenges, this study explores the utilization of waste plastic bottles as reinforcement to enhance the strength of weak clayey soils. Waste plastic bottles were shredded into pieces measuring of 0.5 cm in width and lengths of 1.0 and 1.5 cm. The shredded plastic was incorporated into clayey soil at varying percentages by dry weight (0.5 and 1.0%) with 0.25% increments to determine the optimum dose for maximum dry density (MDD) and corresponding optimum moisture content (OMC). The study also aimed to assess improvements in the California Bearing Ratio (CBR) and shear strength parameters. Standard Proctor tests, Triaxial tests, and soaked CBR tests were conducted to determine the strength properties of unreinforced and reinforced soil samples. The findings revealed a significant increase in MDD, CBR values and shear strength with the inclusion of plastic waste, with the optimum reinforcement dose identified as 0.75% by weight of soil using 0.5 cm × 1.5 cm plastic pieces. This optimum mix exhibited significant strength enhancement, recommending its application in geotechnical engineering in alignment with regulatory standards. The findings also highlight economic advantages, turning environmentally detrimental plastic waste into a valuable material for civil engineering.