Effect of Dynamic Disulfide Bonds on Microstructure, Storage Stability, and Self-Healing Performance of Desulfurized Waste Crumb Rubber–Modified Asphalt

Endowing waste crumb rubber–modified asphalt (CRMA) with superior self-healing capability can extend the service life of asphalt pavement. In this study, 3,3’-dithiodipropionic acid (DPA) with dynamic disulfide bonds was introduced into waste crumb rubber particles through esterification reaction to prepare a novel self-healing crumb rubber–modified asphalt (DPA/CRMA). Fourier-transform infrared spectroscopy results revealed that the dynamic disulfide bonds were successfully connected between crumb rubber particles in DPA/CRMA. With the increase of DPA dosage, the softening point and ductility of DPA/CRMA were gradually increased. The fluorescence microscope images indicated that DPA/CRMA had better dispersibility compared to CRMA. The results of the segregation test showed that the dynamic disulfide bonds in DPA significantly enhanced the storage stability of DPA/CRMA. The results of healing tests showed that DPA improved the self-healing properties of the waste CRMA. The fatigue–healing index and fracture healing rate of DPA/CRMA increased to 96.2 and 69.8%, while those of CRMA were only 67.5 and 46.7%. In addition, dynamic disulfide bonds markedly improved the multiple fatigue–healing capacity of DPA/CRMA, and the number of fatigue–healing cycles for DPA/CRMA was 7, whereas it was only 4 cycles for CRMA. This study provided a new method to extend the service life of waste CRMA pavement.