Preparation Optimization, Rheological Performance and Mechanism of High-Density Polyethylene and Crumb Rubber Composite-Modified Asphalt

The application of crumb rubber (CR) and high-density polyethylene (HDPE) in asphalt modification provides an effective approach to improving binder performance while promoting the sustainable utilization of waste materials. However, differences in the physicochemical characteristics of rubber and polymer modifiers make it challenging to achieve a balance among different performance requirements while maintaining structural stability in the composite system. In this study, an HDPE/CR composite-modified asphalt binder was prepared, and the effects of the preparation process and modifier system on the binder performance were investigated. The orthogonal experimental design was employed to determine the preferred preparation conditions, and the properties of the composite-modified asphalt were evaluated through conventional binder tests, rotational viscosity test, dynamic shear rheometer (DSR) test, multiple stress creep recovery (MSCR) test, bending beam rheometer (BBR) test, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results showed that the preferred preparation process improved the overall performance of the HDPE/CR composite-modified asphalt, including high-temperature deformation resistance, low-temperature crack resistance, and thermal storage-induced separation. The incorporation of auxiliary additives enhanced the dispersion and interaction of the CR and HDPE phases and promoted their interfacial interaction, contributing to the formation of a more stable composite structure. FTIR and SEM analyses revealed that the performance improvement was mainly associated with changes in functional groups, interfacial interactions, and modifier distribution within the asphalt binder. These findings provided insights into the preparation process and modification mechanism of HDPE/CR composite-modified asphalt and demonstrate the potential of combining waste rubber and HDPE to develop high-performance and more sustainable asphalt binders.