This investigation aimed to assess the influence of warm-mix additives on the performance characteristics of recycled asphalt mixtures. Pressure-aging vessels were employed to simulate the aging of asphalt binders. Warm-mix recycled asphalt (WMRA) and mixtures were prepared by incorporating self-developed plant-oil-based rejuvenators and surfactant-based warm-mix additives. The rheological properties of asphalt were tested by a dynamic shear rheometer (DSR). Furthermore, the pavement performance of the asphalt mixture was evaluated by a rutting test, beam bending test, Marshall stability test, and freeze–thaw splitting test. The experimental results demonstrated that the addition of warm-mix additives reduces the penetration and softening point of recycled asphalt while enhancing its ductility. Performance improvement was quantitatively evaluated using a recovery index. The complex modulus and rutting factor of the WMRA were found to be lower than those of recycled asphalt, indicating a decrease in the asphalt’s resistance to deformation owing to the surfactant. Both the hot-mix and warm-mix recycled asphalt mixtures met the specified requirements for various performance indicators. The warm-mix rejuvenator outperformed the regular rejuvenator in evaluating water stability using the soaked Marshall residual stability method, whereas the evaluation based on the freeze–thaw splitting strength ratio demonstrated the opposite trend.

To evaluate the susceptibility of styrene–butadiene–styrene (SBS)-modified asphalt to modifier segregation during high-temperature storage, this study examined its segregation behavior and microstructural evolution under storage conditions ranging from 70 to 163 °C over durations of 48–144 h, with varying warm-mix agent dosages (0%, 3%, 4%, and 5%). The investigation was conducted using softening point measurements, dynamic shear rheometry, infrared spectroscopy, and optical microscopy. The results indicated that the incorporation of the warm-mix agent significantly reduced the difference in softening point, diminished the discrepancies in complex modulus and phase angle between the upper and lower layers, and inhibited SBS aggregation and phase separation. When the warm-mix agent content reached 5%, the softening point difference in the modified asphalt at 163 °C and 48 h decreased from 14.4 °C to 1.6 °C, essentially eliminating segregation. Infrared spectroscopy confirmed that the warm-mix agent did not induce chemical bond changes but improved the compatibility between the SBS modifier and the base asphalt. Microscopic observation further verified that the warm-mix agent facilitated a uniform dispersion of SBS modifier particles, forming a stable microphase structure. The research findings provide valuable insights for improving the storage stability and engineering performance of SBS-modified asphalt.