Performance characterization and mechanistic study of dry process WR/SBS composite modified asphalt mixture

The dry process modification is characterized by simplicity, flexibility, low energy consumption, and low pollution, making it an ideal choice in pavement repair engineering. This study aims to optimize the use of waste rubber powder and SBS modifiers in dry process composite modification by preparing dry process W R /SBS composite modified particles (W R /SBS CMP) using a twin-screw extruder. The optimum mixing content of modified particles was determined through comparative analysis of pavement performance of dry process W R /SBS composite modified, wet-process SBS-modified, and matrix asphalt mixtures. The rheological properties and modification mechanism of the asphalt binder extracted from these mixtures were tested and analyzed. The results indicate that when the content of dry process W R /SBS CMP is 2.3 % of the aggregate weight in the mixture, the comprehensive pavement performance of the dry process composite-modified asphalt mixture is optimal. Melt extrusion granulation at high temperatures, along with the addition of additives such as naphthenic and aromatic oils, promoted the degradation and refinement of the rubber powder and SBS, improving their compatibility and dispersion within the asphalt binder. The modified particles uniformly interact with the asphalt binder, increasing the proportion of elastic components, reducing stress sensitivity, and enhancing performance at both high and low temperatures, and fatigue resistance. Fourier Transform Infrared Spectroscopy (FTIR) confirmed that the modification mechanism was a physical modification. This research promotes the broad application of waste rubber powder and dry process modification in asphalt mixtures, offering significant economic and social benefits. • A novel dry-process W R /SBS composite particles was developed via twin-screw melt blending. • Modification mechanism of asphalt mixtures with dry-process W R /SBS CMP was revealed. • The optimum content of modified particles was determined by the mixture performance optimization.