Influence Mechanism of Performance and Aging Behavior of High-Content SBS-Modified Asphalt

To address the research bottlenecks in the performance mechanism and engineering application of high-content SBS-modified asphalt (SBS content ≥ 6%), this study used 70# and 90# base asphalts as raw materials to prepare modified asphalts with SBS contents of 5%, 8%, 10%, and 12% via a high-speed shearing-stirring process. Combined with conventional performance tests (penetration, ductility, elastic recovery), rheological analysis (dynamic shear rheology (DSR), rotational viscosity), and micro-characterization (Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS)), the regulatory mechanisms of SBS content, base asphalt type, and aging process (RTFOT short-term aging, PAV long-term aging) on asphalt performance were systematically investigated. The results showed that with the increase in SBS content, the asphalt’s increased consistency (as indicated by decreased penetration), low-temperature crack resistance (5 °C ductility increased by more than 5 times), and high-temperature rutting resistance (60 °C complex shear modulus G* increased by 17 times) were significantly enhanced. Due to its higher content of light components, the 90# base asphalt exhibited a better modification effect than the 70# base asphalt. At 12% SBS content, the 5 °C ductility and 60 °C G* of the 90# base asphalt system reached 49.42 cm and 41.62 kPa, respectively. High-content SBS optimized the viscoelastic balance of asphalt: the 70# base asphalt system with 10–12% SBS content showed a phase angle δ < 45° (elasticity-dominated), and the modified asphalt with 12% SBS content exhibited a decrease in fatigue factor (G*sinδ) after PAV aging, indicating excellent fatigue resistance stability. The aging process significantly increased asphalt viscosity (the viscosity of 70# base asphalt with 10% SBS increased by 242% after PAV aging at 135 °C), while high-content SBS inhibited aging deterioration—the penetration ratio of both systems exceeded 96% at 10% SBS content. At the microscale, 10% SBS content enabled the asphalt to form a continuous and dense network structure, reducing carbon loss and slowing oxygen incorporation. Based on PG classification, the modified asphalt with 12% SBS content reached the PG100 grade, which can meet the needs of heavy-load and high-temperature scenarios such as high-toughness ultra-thin asphalt wearing courses. This study provides a key theoretical basis and data support for the content design and engineering promotion of high-content SBS-modified asphalt.