Stability of Repurposed Plastics in Asphalt Binder

Five types of waste plastic streams were investigated for their compatibility with a PG 64-22 asphalt binder. The waste plastics included high-density polyethylene (HDPE) pails; low-density polyethylene (LDPE) food packaging waste; polypropylene (PP) from various waste sources, such as plastic cups, medicine bottles, blackboards, and whiteboards; polystyrene (PS) from food packaging; and plastic number 7 from various sources, including polycarbonate, CD cases, and polycarbonate fibers. The plastics were characterized using Fourier-transform infrared spectroscopy (FTIR). Thermogravimetric analysis was performed to optimize the blending. Storage stability of waste plastic-modified binders was evaluated using the cigar tube test (CTT). Rheological and multiple stress creep recovery (MSCR) tests were performed for predicting rutting and cracking potential. No significant chemical changes were noticed when plastics were added to the binder. However, some of the waste plastic-modified binders appeared to be unstable. The rheological properties of waste plastic-modified binder vary with respect to unmodified binder; most plastics exhibited degradation. The MSCR test showed no improvement in the elasticity of the nonrecoverable strain for tested waste plastic-modified binders. This suggests that wet mixing of waste plastic with binder could be ineffective in some cases.