## 5 Conclusions  
A simultaneous variation in the contents of the bee phase and bee casing was realized via finite element simulation to explore the influence of internal microstructural changes on the micromechanical behavior of an asphalt binder in the aging and rejuvenation process, which provided theoretical references for the application of a regenerated asphalt binder, and several conclusions were obtained as follows:  
1. The stress in the bee phase is significantly greater than that in the bee casing, and the stress in the interstitial phase is minimal. When the asphalt binder is aged, the proportions of the bee phase and bee casing increase, which will produce greater internal stresses within the asphalt binder, which, in turn, is more prone to fatigue cracking and other problems. 2. With the simultaneous increase in the contents of the bee phase and the bee casing, the stress in each phase structure in the asphalt binder samples increase. The stress of the interstitial phase increases at the fastest rate, and the stresses of the bee phase and the bee casing increase at a similar rate. The rejuvenation level of the aged asphalt binder has not yet reached the upper limit, and with the increase in the dosage of the old material, its interfacial interaction capacity with the new asphalt binder also gradually increases, leading to an increase in the interfacial bee casing, and a gradual increase in the internal stress of the recycled asphalt binder. 3. Under the combined effect of the decrease in the proportion of bee phase and the increase in the proportion of the bee casing, there is a certain degree of increase in the internal stresses and strains in the asphalt binder, the effect of the bee casing on the internal stresses in the asphalt binder is more pronounced, and the bee phase and the bee casing play a better role in resisting external deformation due to the increase in the volume fraction. When the aged asphalt binder in the rejuvenation process gradually interacts with the unaged asphalt binder, part of the aged asphalt binder and the unaged asphalt binder are fused together to form an interfacial phase (bee casing), resulting in a decrease in the aged asphalt binder and an increase in the interfacial phase, and at this time, the internal stress of the regenerated asphalt binder becomes larger. 4. Under the action of a displacement load, the internal tensile strain of the asphalt binder increases, the magnitude of strain increases with the increase in old material mixing, and the interstitial phase is the most sensitive. For a recycled asphalt binder, whether it is used to improve the old material doping or to enhance the new and old asphalt binders' interfacial diffusion fusion, it will, to a certain extent, increase the level of tensile strain within the recycled asphalt binder, which, in turn, puts forward higher requirements for its anti-cracking properties. **Author Contributions:** Conceptualization, M.G. ; methodology, D.L. ; software, D.L. ; validation, X.Y. and D.H.; formal analysis, X.Y. ; investigation, X.Y. ; resources, D.L. ; data curation, D.L. ; writing--original draft preparation, D.H. and D.L. ; writing--review and editing, D.H. and X.Y. ; visualization, M.G. ; supervision, M.G. ; funding acquisition, M.G. All authors have read and agreed to the published version of the manuscript. **Funding:** The authors would like to acknowledge that this paper was financially supported by the National Key Research and Development Program of China (2022 YFE0137300) and the National Natural Science Foundation of China (52078018). **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** The data presented in this study are conditionally available upon request to the corresponding authors. **Acknowledgments:** We are grateful to RWTH Aachen University, Germany, for discussing exchanges and for helping us with model building, parameter setting, and setting the contents of bee phase and shell in the simulation.