Effect of maleic anhydride grafted and gamma-irradiated waste polypropylene on rheological properties of asphalt binder

Waste polymers have been employed as a modifier in bitumen to improve the performance of the binders and reduce plastic pollution. Grafting of maleic anhydride (MA) is a method to increase the chemical and physical consistency between the polymer and binder. In this study, maleic anhydride grafted waste polypropylene was employed as a bitumen modifier. Gamma irradiation is applied to waste polypropylene to improve the compatibility. The effects of MA-grafted irradiated waste polypropylene (PPR-γ-MA) on physical and rheological properties of bitumen were investigated through a test program. Storage stability tests signifies that the gamma irradiation could diminish the phase separation between the modifier and bitumen. The thermorheological tests showed employing PPR-γ-MA improves the high temperature performance, whilst it has a slightly adverse effect on low temperature performance of bitumen. The results of multiple stress creep recovery (MSCR) test indicate that PPR-γ-MA reduces the non-recoverable deformation and enhanced elastic recovery of the material, whereas the linear amplitude sweep (LAS) test result signifies PPR-γ-MA improved the fatigue life of asphalt by increasing fatigue damage resistance under different strain levels. The rheological test results emphasised on the usability of PPR-γ-MA as a modifier in binders.