Development of sustainable desulfurized waste crumb rubber modified asphalt with enhanced self-healing properties

Developing waste crumb rubber modified asphalt (CRMA) with enhanced self-healing properties can improve the crack-healing ability of asphalt, which is conducive to extending the service life of asphalt pavements. The objective of this study is to introduce dynamic disulfide bonds into desulfurized waste crumb rubber and to prepare two types of intrinsic self-healing waste crumb rubber modified asphalt by the breakage-rearrangement effect of dynamic disulfide bonds. Chemical structure analysis revealed that through the esterification reaction between -COOH in dithiodipropionic acid (DPA) and dithiosalicylic acid (DTSA) and -OH in desulfurized waste crumb rubber, DPA/CRMA with aliphatic disulfide bonds and DTSA/CRMA with aromatic disulfide bonds were successfully prepared. The results of the healing tests showed that DPA/CRMA and DTSA/CRMA exhibited better healing properties due to the breakage-rearrangement effect of dynamic disulfide bonds. The fatigue healing indices of DPA/CRMA and DTSA/CRMA were 31.3 % and 36.3 % higher than those of CRMA. The fracture healing rates of DPA/CRMA and DTSA/CRMA were enhanced by 67.6 % and 79.9 % compared to CRMA. The rheological test results revealed that DPA/CRMA exhibited better cracking resistance both before and after aging compared to DTSA/CRMA. Overall, the DTSA/CRMA exhibited better self-healing performance due to the lower bond energies and stronger breakage-rearrangement effect of the aromatic disulfide bonds, while the DPA/CRMA had better cracking resistance.