The diffusion between the virgin and aged asphalt binder in the recycled asphalt mixture is a crucial factor affecting its macro-mechanical performance. In this study, a combined model of the virgin-aged layered asphalt structure was assembled based on the molecular dynamics (MD) method. A four-component and twelve-category molecule were used to model the asphalt. The diffusion behaviors of the virgin and aged asphalt were characterized by mean square displacement (MSD), diffusion coefficient, relative concentration and cohesive energy density (CED). Results indicated that at the same temperature, the diffusion coefficient of the virgin asphalt was the largest, followed by the virgin-aged asphalt and the aged asphalt. As the temperature increased, the relative concentration on both sides of the virgin-aged asphalt overlapped to a certain extent. The covered lengths of the virgin asphalt were larger than those of the aged asphalt, indicating the diffusion between the virgin asphalt and aged asphalt was mainly manifested as the diffusion from the virgin asphalt to the aged asphalt. The development of CED and the fraction of free volume (FFV) indicated the mutual attractive interactions among the molecules in virgin and aged asphalt layers became strong and the cohesion properties inside the model became better.

In order to address the influence of aging on the performance degradation of SBS‐modified asphalt, a composite modification of SBS‐modified asphalt by nano‐zinc oxide (nano‐ZnO) and Trinidad Lake asphalt (TLA) was proposed. Several tests were conducted after adding nano‐ZnO and TLA to SBS‐modified asphalt, including a rotary film oven test (RTFOT), ultraviolet aging (UV), and the pressure aging vessel test (PAV). The conventional physical index, rheological index, and four‐component content of SBS‐modified asphalt before and after three aging modes were tested, and the characteristic functional groups in SBS‐modified asphalt were tracked and analyzed by Fourier transform infrared spectroscopy (FTIR). The results show that the effects of aging on the rheological properties of SBS‐modified asphalt are clearly reduced by adding different proportions of nano‐ZnO and TLA in the process of thermal oxygen aging and the ultraviolet aging test, and the antiaging ability of SBS‐modified asphalt is clearly improved. To improve the conventional performance and rheological properties of SBS‐modified asphalt, an incorporation ratio of 3% nano‐ZnO + 25% TLA was proposed. At the same time, the increased rate of heavy components and the change index of the colloidal instability index in the SBS‐modified asphalt under the blending ratio were significantly lower than the blank SBS‐modified asphalt samples in the same aging mode. FTIR spectra also showed that SBS‐modified asphalt performance deterioration were mainly caused by long‐term aging and ultraviolet aging. The addition of nano‐ZnO and TLA effectively reduced the increase of carbonyl groups and the breakage of the C=C double bond in butadiene and synergistically improved the comprehensive aging resistance of SBS‐modified asphalt. Therefore, the use of this modification is an effective method to solve the aging problem of SBS‐modified asphalt.