Recyclability potential of waste plastic-modified asphalt concrete with consideration to its environmental impact

The use of waste plastic into asphalt concrete paving mix (ACP) has been explored in recent literature to improve the functional properties of the mix. However, exploration on their recyclability potential at the end of its service life remains scarce. This study explores the potential of recycling aged waste plastic-modified asphalt concrete (AACP) for road pavements, with focus on four commonly disposed household plastics: high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS) and polyethylene (PET). Marshall stability test, Cantabro abrasion test, indirect tensile strength test, resilient modulus (MR) test, Hamburg's wheel tracking test and stripping test were performed to evaluate the engineering properties of recycled waste plastic-modified asphalt concrete (RACP) containing proportions ranging from 20 % to 100 % aged component (AACP) blended with virgin mixtures. This paper highlights significant engineering performance of RACP, and most notably for RACP containing PP with 20 % aged content which exhibits 1.6 times greater resistance to moisture damage compared to conventional recycled asphalt concrete (RAPA). Although RACP with HDPE and PP (consisting of 20 % and 40 % AACP in mix) yield improvements in resilient modulus over RAPA, this improvement is less pronounced for RACP with PS and PET. Overall, RACP with 40 % aged components exhibits better rutting, moisture damage and abrasion loss performance, along with improved stability and flow value. Environmental impact in terms of water leachability was also found to be negligible in this study and RACP can be considered a feasible sustainable pavement material, with potential for second and more lives.