Impacts of Low-Density Polyethylene (Plastic Shopping Bags) on Structural Performance and Permeability of HMA Mixtures

This paper examines the optimum contents of bitumen (by weight of aggregates) and Low-Density-Polyethylene (LDPE) plastic (by weight of bitumen) to ensure the long-term performance of HMA mixtures. The coefficient of permeability of HMA samples with different contents of bitumen and LDPE was estimated to understand rainwater infiltration rate. The Marshall Mix Design Procedures ASTM D1559-76 were applied to estimate the Marshall stability and flow values. The falling head method of permeability test estimates the water infiltration rate. The results show that the optimum bitumen content (5.5-6% by weight of aggregates) with higher contents (15% by weight of bitumen) of plastic materials increase structural stability, reduce permanent deformation, increase ductility, and improve fatigue life of HMA mixtures. This study also finds that permeability of HMA mixtures decreases rapidly for 4% to 4.5% of bitumen contents. Impermeability for all type of HMA mixtures increases slightly with 1% to 4% air voids. Findings of this study complement to studies on plastic materials in bituminous pavements such as: (1) estimation of optimum contents of both bitumen and plastic materials in HMA mixtures and (2) estimation of permeability coefficients with different proportion of both bitumen and plastic contents to understand the impacts of plastic materials on the permeability of bituminous pavement.