This study presents a modification strategy to fabricate core–shell composite aggregates from reclaimed asphalt pavement (RAP), aligning with green chemistry principles for waste valorization. The method involves creating a porous cementitious shell on the surface of RAP particles through a controlled hydration process. This surface modification simultaneously addresses the inherent structural weaknesses and irregular morphology of raw RAP, enabling the design of materials with desired properties. A face-centered central composite design (FCCD) was employed to optimize the synthesis process, elucidating the nonlinear relationships between key synthesis parameters and the final material characteristics. The optimized synthesis yielded porous aggregates with significantly enhanced structural integrity, evidenced by a 43.9% reduction in crushing value. Furthermore, the surface modification effectively regulated the material’s morphology and particle size distribution, leading to a 3.6 mm increase in median particle size (D₅₀) and a 27.69% decrease in the content of fines (<4.75 mm). Microstructural characterization confirmed the formation of a rough, porous cementitious shell composed of hydration products, which provides the structural basis for the material’s enhanced performance. This work establishes a clear structure–property relationship, demonstrating a new pathway for the rational design and synthesis of functional porous materials from solid waste for application in high-grade pavements.

Capsaicin is an amphiphilic organic molecule containing both a hydrophobic hydrocarbon chain and polar functional groups, giving it the potential to regulate the surface wettability and interfacial interactions of organic materials. To evaluate capsaicin as an interfacial modifier for improving the anti-icing performance of asphalt binder, capsaicin-modified binders with different dosages were prepared and systematically characterized in terms of conventional properties, high- and low-temperature rheological performance, chemical structure, surface wettability, and water-droplet freezing and melting-induced shedding behavior. Capsaicin was incorporated into the asphalt matrix mainly through physical blending and moderately increased the high-temperature stiffness. At an appropriate dosage, the low-temperature creep and stress-relaxation properties were also improved. The addition of capsaicin increased the water contact angle and reduced the total surface free energy, thereby weakening water spreading and water-asphalt interfacial interactions. At temperatures from −5 to −20 °C, all modified binders exhibited delayed complete freezing and facilitated the gravity-driven shedding of frozen droplets during melting at room temperature. Pearson correlation analysis further showed that longer freezing times and shorter ice-shedding times were closely associated with a larger water contact angle and lower surface free energy. Additional validation after long-term aging confirmed that the surface-regulation and freezing-shedding effects of capsaicin remained effective after aging. Considering both binder performance and freezing-shedding behavior, a capsaicin dosage of 12% provided the best overall balance. These findings identify capsaicin as a promising interfacial modifier for the design of anti-icing asphalt materials.