Design and Formulation of Waste Plastic Materials with Asphalt for Road and Pavement Construction

Abstract

The rapid increase in plastic waste generation poses serious environmental, social, and economic challenges, particularly in developing countries such as Nigeria, where disposal infrastructure is inadequate. This study investigates the design and formulation of hot mix asphalt incorporating waste polyethylene terephthalate (PET) and high-density polyethylene (HDPE) for road and pavement construction. Using the dry mix method, PET and HDPE were processed to 2–4 mm and blended with 70/80 penetration grade bitumen and aggregates at 2%, 3%, 4%, 5%, and 6% by weight of the mix. Thirty Marshall specimens were prepared and evaluated for stability, flow, voids, voids filled with bitumen (VFB), and density in accordance with ASTM D1559. Results revealed that asphalt mixes containing PET and HDPE exhibited improved stiffness and resistance to rutting relative to the control. Optimal performance was observed at 2–4% plastic content. PET mixes showed higher Marshall Stability at 6% (4.70 kN) and higher VFB (81.42%) compared with HDPE. The incorporation of plastic waste offers significant environmental benefits by diverting waste from landfills and reducing binder demand, while also offering potential cost savings and extended pavement lifespan. The study concludes that integrating PET and HDPE into asphalt pavement is a viable, sustainable approach, but recommends standardisation, durability testing, and field-scale validation.