Study on Rheological Behavior and Modification Mechanism of SBS/Tackifying Resin Composite High-Viscosity Modified Asphalt

To investigate the rheological properties of poly(styrene-butadiene-styrene) (SBS)/tackifying resin composite high-viscosity modified asphalt, a single-factor control variable method was used to study the influence of modifiers content. The conventional properties, 60°C dynamic viscosity, 135°C rotational viscosity, and elastic recovery of the modified asphalt was systematically evaluated. Meanwhile, the rheological properties, modification mechanism, and microstructure of composite-modified, high-viscosity asphalt were thoroughly analyzed by dynamic shear rheometry, Fourier transform infrared spectroscopy, fluorescence microscopy, and atomic force microscopy. The results showed that the optimal proportion for composite modification was 7.5% SBS modifier, 0.19% stabilizer, 3% tackifier A, and 1% tackifier B. The addition of tackifiers A and B significantly improved the high-temperature performance and rutting resistance of the asphalt, satisfying the requirements of overweight traffic and above levels. After adding tackifier A, the C─ H aromatic stretching vibration at 3,042 cm−1 of the asphalt disappeared. Tackifier A increased the polarity between components, which caused coupling to occur inside the composite-modified, high-viscosity asphalt, forming a uniform network distribution among the asphalt and optimizing the compatibility between modifiers and asphalt, which improved the viscosity and performance. The network structure in the A/B composite-modified, high-viscosity asphalt system was more stable, and the root mean square roughness, Rq, of A/B2# asphalt was 1.36 nm, showing the best compatibility within the asphalt.