Influence of modifiers components on rheological properties of waste plastic-rubber modified asphalt

The use of waste materials in asphalt binders is an important strategy for sustainable pavement construction, but the stability of waste plastic-rubber modified systems is still limited by poor interfacial compatibility. This study investigates the influence of the modifier composition (plastic-to-rubber (P/R) ratio) and the concentration of the SEBS-g-MA compatibilizer (2.5 wt.%−7.5 wt.%) on the interface structure and rheological properties of waste plastic-rubber modified asphalt. Reactively extruded composites were characterized using gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR) to evaluate molecular-weight evolution and ester-related chemical interactions, while binder performance was assessed through storage stability, viscosity, and rheological testing under both linear viscoelastic (LVE) and nonlinear viscoelastic (NLVE) conditions. The results showed that the 5.0 wt.% SEBS-g-MA concentration maximizing both chemical crosslinking and rubber devulcanization rates. Performance evaluations demonstrated that a 7.5 wt.% SEBS-g-MA concentration provided excellent storage stability (SI < 7.1%) to the asphalt due to the enhanced physical entanglement between the composite components. The master curve indicated that the asphalt binders with more rubber (PRA1:4) exhibited superior stiffness and elasticity. However, the results of the multiple stress creep and recovery (MSCR) test showed that the PRA1:3 samples with lower rubber content showed better rutting resistance ( J nr =0.45 kPa −1 to 0.65 kPa −1 ) and recovery ( R >25%). These findings demonstrate that the performance of waste plastic-rubber modified asphalt is governed by the combined effects of compatibilizer-induced interfacial evolution and P/R ratio and highlight the importance of evaluating both LVE and NLVE responses to understand mechanism–performance relationships in compatibilized waste-material asphalt systems.