AbstractThe continuous pollution of waste plastics to the ecological environment has attracted global attention. Using waste plastics in road construction can save energy, reduce pollution, and improve the high-temperature performance of asphalt mixtures. It will be the development trend of road materials in the future, but there have been few in-depth studies and evaluations on it. This study evaluated the microscopic characteristics of waste plastic modified asphalt. After the investigation and screening, this study used low-density polyethylene (LDPE) recycled materials in waste plastics as the main research object and used twin-screw extruders and instant dispersants to directly modify them and optimize the modification process parameters. In this way, a direct throw-in type of waste plastic asphalt modifier was prepared. Through fluorescence microscopy, infrared spectroscopy, scanning electron microscopy, gel chromatography, X-ray diffraction methods (XRD), and other technical means, the modification mechanism of direct-input waste plastic modified asphalt was analyzed. The test results show that the direct-input waste plastic modifier can achieve micron-level dispersion in the asphalt under the action of the instant dispersant, which can significantly improve the high-temperature performance of the asphalt mixture.