Bonding Behavior and Aging Evolution Mechanism of The Asphalt–Aggregate Interface Modified by Pre-vulcanized Natural Latex

Abstract To reveal the influence of pre-vulcanized natural latex on the interfacial bonding behavior and aging stability of asphalt–aggregate, this paper uses 90# base asphalt, unvulcanized natural latex-modified asphalt, and pre-vulcanized natural latex-modified asphalt as research objects, and selects three typical aggregates: granite, basalt, and limestone. In this study, RTFOT short-term aging and PAV long-term aging were combined with AFM, BBS, μTS, and contact angle measurements to comprehensively characterize the micro-morphology, surface adhesive behavior, interface bonding performance, and surface free energy properties of various asphalt. The findings indicate that natural latex incorporation enhances the adhesive characteristics of asphalt surfaces. However, when latex is not vulcanized, phase rearrangement and localized aggregation may occur under prolonged aging conditions, thereby weakening the stability of interfacial bonding. In contrast, pre-vulcanized natural latex can promote the formation of a finer and more uniform dispersed phase structure in asphalt and effectively limit the migration of the rubber phase and component aggregation during the aging process. AFM-QNM results showed that the adhesion strength of A2-PAV remained at 67.6710 nN, significantly higher than that of A0-PAV and A1-PAV, while its DMT modulus was lower, indicating that the pre-vulcanized system can delay aging hardening and maintain good surface adhesion. BBS and μTS results further demonstrated that pre-vulcanized natural latex-modified asphalt exhibited higher static interfacial load-bearing capacity at low temperatures and after aging. Surface free energy results showed that the overall interfacial adhesion strength of different aggregates was limestone > basalt > granite, and the A2 system maintained a high adhesion work under different aging conditions. Overall, pre-vulcanized natural latex can enhance the asphalt–aggregate interfacial bond performance by improving the microstructure, maintaining surface adhesion, and improving interfacial anti-aging stability. These findings provide a basis for the application of natural latex modified asphalt in durable pavement materials.