Rutting and Aging Resistance of Bitumen Modified by Polyethylene, Polypropylene, and Their Cross-Contamination

Abstract

The use of recycled plastic in modifying bitumen has attracted considerable attention in recent years. However, uncertainties remain about the impact of polymeric cross-contamination on bitumen modification. This study investigates the influence of high-density polyethylene (HDPE) and polypropylene (PP), and their cross-contamination, on the rutting performance and aging properties of bitumen. This study also evaluates the appropriateness of standard asphalt binder test methods for characterizing the rutting performance of bitumen modified with waste plastics. This study showed that multiple stress creep recovery (MSCR) is the most suitable technique to differentiate the improvements in rutting resistance achieved by modifications with different waste plastics. The outcome of this study demonstrated that polymeric cross-contamination between HDPE and PP can result in significant variations in bitumen properties and performance. MSCR revealed that PP modification upgraded the rutting performance of bitumen by two grades, whereas HDPE and the blend of the two plastics upgraded the bitumen by one grade. Rheological assessments, including Black diagram and Cole-Cole plots, showed that PP significantly enhanced bitumen elasticity, which was not observed by HDPE or the blend of the plastics modification. Aging analysis demonstrated superior resistance to aging with HDPE and the blend compared to PP, confirmed by the Black diagram and TGA results.