Balance optimization of high and low temperature performance for crumb rubber-LDPE-EVA composite modified asphalt binder

Valorizing waste rubber and plastics in pavement engineering enhances sustainability. However, binary binders combining crumb rubber (CR) and mono-component plastics often struggle to balance high temperature rutting resistance and low temperature flexibility. This study aims to explore synergistic effects of ethylene-vinyl acetate (EVA), CR, and low-density polyethylene (LDPE) on optimizing this balance. First, the CR-LDPE modifier (RPM) was prepared, with its optimal preparation conditions determined by orthogonal experiments. Then, the optimum blending proportion of the CR-LDPE-EVA composite modified asphalt binder (RPMA-E) realized by response surface method (RSM). Subsequently, the macroscopic rheological behaviors and microscopic synergistic mechanisms of the ternary modifier system were systematically characterized utilizing high and low temperature rheological tests, fluorescence microscopy (FM), and fourier transform infrared spectroscopy (FTIR). Ultimately, a comprehensive evaluation based on the Analytic Hierarchy Process (AHP) was conducted to screen for the modified asphalt binder possessing balanced rheological performance. The investigation indicated that optimal preparation of the CR-LDPE modifier occurs at an extrusion temperature of 240 ℃, utilizing a 7:3 mass ratio of CR:LDPE and 2% desulfurization additive. Moreover, the most effective binder formulation was identified as containing 18% RPM, 4% EVA, and 3.7% compatibilizer. The combined application of RPM and EVA markedly improved the high temperature stiffness of the binder. Meanwhile, the addition of EVA and compatibilizer enhanced low temperature crack resistance and reduced segregation at the softening point, where EVA exhibited a particularly pronounced stabilizing effect. The AHP analysis confirmed that the 18% RPMA-E successfully attains the optimal compromise between high temperature stability and low temperature flexibility.