Characteristics of the Rheology and Microscopic Mechanism of Asphalt Damage Under the Influence of Multicomponent Couplings

As the core binder material of asphalt pavement, the rheological properties of asphalt directly determine the service performance and service life of the pavement. Under actual service conditions, asphalt is constantly exposed to a multi-coupling environment involving temperature variation, vehicle load, and ultraviolet aging, which easily leads to irreversible rheological deterioration and induces diseases such as rutting and cracking. Aiming at the insufficient research on the rheological evolution law and microscopic damage mechanism under the coupling of the above three factors, this study took 70# base asphalt as the research object and adopted a combination of macro-performance testing and microstructure characterization. The high- and low-temperature rheological properties, permanent deformation resistance, and fatigue resistance of asphalt under multi-coupling effects were systematically evaluated through three conventional index tests: dynamic shear rheology (DSR), multiple stress creep recovery (MSCR), linear amplitude sweep (LAS) and bending beam rheology (BBR). Combined with gel permeation chromatography (GPC) and thin-layer chromatography with flame ionization detection (TLC–FID), the evolution laws of molecular distribution and chemical components were revealed, and the deterioration mechanism of multi-coupling effects was clarified. The results show that compared with the control group, after 72 h of coupling treatment, the penetration decreases by 32.6%, the softening point increases by 18.3%, and the ductility decreases by 45.8%. The high-temperature complex modulus decreases by 51.2%, the low-temperature creep stiffness increases by 76.4%, and the fatigue life decreases by 58.6% on average. At the microscopic level, obvious molecular polymerization and component weight gain occur in asphalt: the content of macromolecular components rises from 18.7% to 32.1%, asphaltene content increases from 12.3% to 25.8%, and aromatic content decreases from 42.6% to 28.3%. Temperature variation, load, and ultraviolet aging present significant deterioration effects, rather than a simple superposition of single factors. Prolonged aging and increased load aggravate the hardening of asphalt, while extreme temperature variation further weakens the rheological properties through microscopic damage. This study clarifies the internal relationship between the microscopic structure and macroscopic properties of asphalt under multi-coupling effects, improves the theory of anti-coupling damage to asphalt, and provides an important theoretical basis and experimental support for damage-resistant design, material selection, and service life prediction of asphalt pavement.