Performance of Dry Mixed Rubber–Plastic Composite Modified Asphalt Mixture

In wet process–modified asphalt, the modifier is easily separated from the asphalt, resulting in poor storage stability. For traditional dry-mixed modified-asphalt mixtures, adding a single modifier to the mixture, it is difficult to improve the comprehensive performance of asphalt mixtures. In this study, rubber–polyethylene composite modified particles were added to a dry-mixed asphalt mixture. The rubber powder was first desulfurized using a twin-screw extruder and then blended and extruded with low-density polyethylene particles to form rubber–plastic composite particles. Then, the high- and low-temperature performance and water stability of the dry-mixed rubber–plastic composite modified asphalt mixture were evaluated. Finally, the asphalt in the rubber–plastic composite modified mixture was extracted. The microscale properties were tested to investigate the mechanism of the composite particles. The results indicated that the rubber–plastic composite modified particles improved the high-temperature deformation resistance of the mixture. Additionally, the low-temperature crack resistance and water stability were slightly improved. Compared with adding desulfurized rubber powder alone, the comprehensive performance of the asphalt mixture can be significantly improved by using a rubber–plastic composite.