Enhancing rheological properties and durability of asphalt binders with orthogonal-optimized composite modifier particles prepared via twin-screw extrusion: Performance and mechanisms

To address the intrinsic limitations of conventional polymer-modified asphalt binders, including high-temperature aging susceptibility, energy-intensive processing, and compromised storage stability, this study developed orthogonal-optimized composite modifier particles (CMPs) via an L9 (3 3 ) orthogonal design and twin-screw extrusion, integrating styrene-butadiene-styrene (SBS), compatibilizer, tackifying resin (TR), and inorganic crosslinking agent (ICA). The comprehensive performance of CMPs-modified asphalt was systematically evaluated by means of conventional, rheological, and microstructural characterization tests. Results showed CMPs-modified asphalt exhibits significantly superior thermal storage stability to conventional SBS-modified asphalt, with all segregation values below 2.5 °C. CMPs formulations T-9, T-4, and T-2 exhibited superior high-temperature deformation resistance, low-temperature cracking resistance, and fatigue resistance. FTIR analysis confirmed the formation of C–S bonds, and fluorescence microscopy showed continuous polymer networks. Economic analysis confirmed T-9 had the highest cost-effectiveness. This granulation strategy reduced processing temperatures by more than 10°C versus conventional SBS modification, aligning with sustainability goals. This work provides a scalable, eco-efficient solution for high-performance asphalt pavements under extreme climates and heavy loads.