Polymer Ca-alginate capsules with rejuvenator bring a high healing level for asphalt concrete under dry healing environments; however, the healing levels of bituminous mixtures containing capsules under water healing conditions are still unknown. In view of this, this study aimed at exploring the healing levels of asphalt concrete containing polymer capsules under various solution healing conditions following cyclic loads. This study involved the preparation of capsules, followed by the evaluation of their morphological characteristics, resilience to compression, thermal endurance, and rejuvenator content. The assessment of the healing properties of asphalt concrete utilizing capsules was conducted through a fracture–heal–refracture examination. This study conducted Fourier transform infrared spectrum experiments to determine the rejuvenator release ratio of capsules under dry conditions and the remaining rejuvenator content in extracted bituminous binder from capsule–asphalt concrete after solution treatment. Meanwhile, a dynamic shear rheometer was utilized to investigate the rheological characteristics of asphalt binder. Results revealed that the healing ratios of capsule–asphalt concrete beams under a dry healing environment were significantly higher than that of beams under various solution healing conditions, and the alkali solution has the worst effect on the improvement in healing ratio. The coupled impact of moisture intrusion and ion erosion resulted in an enhancement of complex modulus of asphalt binder while concurrently reducing its phase angle. Consequently, the restorative capacity of the asphalt binder was weakened.

Using solid waste to replace limestone filler in asphalt concrete can not only reduce the cost of road construction, but also improve the utilization rate of solid waste. In this study, PHC pile waste concrete (PPWC) was innovatively used to replace limestone filler in asphalt mixture and its effect on the physical and rheological properties of asphalt mastics was studied. Firstly, PPWC was ground into filler particles with a diameter less than 0.075 mm. The physical properties, particle characteristics and chemical composition of PPWC filler and limestone filler were compared. Asphalt mastics were prepared with different filler-asphalt volume ratios (20%, 30% and 40%) and the physical properties, high-temperature rheological properties and low-temperature cracking resistance of asphalt mastics were tested. The experimental results showed that the surface of PPWC filler is rougher and has lower density and smaller particle size than limestone filler. When the filler content is the same, PPWC filler asphalt mastics have lower penetration and ductility, higher softening point than limestone filler asphalt mastics, and the viscosity of PPWC filler asphalt mastics is more sensitive than limestone filler asphalt mastics. PPWC filler asphalt mastics demonstrated superior high-temperature stability, but poorer low-temperature cracking resistance compared to limestone filler asphalt mastics. In conclusion, PPWC fillers can be used to replace limestone fillers in asphalt mixtures. The finding of this study will provide a new solution for the construction of eco-friendly roads.

Damp-heat environments significantly accelerate the aging and performance deterioration of asphalt pavements. This study systematically evaluated the performance evolution of base and SBS-modified asphalt binders, as well as their corresponding steel slag and basalt asphalt mixtures, under diverse damp-heat aging conditions (60–80 °C, 90% RH, 0–8 days). Physical and rheological characterizations indicate that base asphalt exhibits a monotonic hardening law during damp-heat aging, whereas SBS-modified asphalt demonstrates a unique two-stage aging process characterized by initial softening followed by hardening. Chemical functional group analysis further confirms that damp-heat aging results from the synergistic effects of early-stage moisture ingress and long-term thermal-oxidative hardening—a process effectively delayed by the SBS polymer network. Furthermore, microscopic morphology and elemental analysis reveal that steel slag aggregates establish a robust dual mechanism to resist moisture erosion through the mechanical interlocking of surface micropores and the chemical anchoring of alkaline constituents. A comprehensive evaluation using the improved radar chart method (f-value) further substantiates that steel slag not only enhances the initial performance of the mixtures but also significantly reduces their time–temperature sensitivity to damp-heat environments. Finally, full-scale field applications in damp-heat regions demonstrate that steel slag asphalt pavements maintain a residual Marshall stability of 87.6% and a texture depth retention rate of 91.5% after service. These results indicate superior early-to-mid-term moisture damage resistance and safety compared to basalt-based pavements, providing critical theoretical and practical support for material design and performance improvement in extreme damp-heat climatic regions.