In order to study the high and low temperature properties, and fatigue properties, of silica fume/SBS (Styrene-Butadiene-Styrene) compound modified asphalt (SFSCMA), dynamic shear rheometer (DSR) and bending beam rheometer (BBR) are used to study matrix asphalt (MA), silica fume modified asphalt (SFMA) (silica fume (SF) 6%), SBS modified asphalt (SBSMA) (mass ratio of SBS to Matrix asphalt 4%), and silica fume/SBS compound modified asphalt, and the high temperature rheological properties of silica fume/SBS compound modified asphalt with different silica fume additions are also studied. The modification mechanism of SFSCMA was studied by scanning electron microscope (SEM). The investigation results turn out: along with the increase in the content of SF, the high temperature performance of SFSCMA is improved significantly. When the content of SF is 6%, the high temperature performance is the best. When the content of SF is more than 6%, the high temperature property of SFSCMA is lower than that of SBSMA. It is suggested to choose 6% as the content of SF. Compared with MA, SFMA, and SBSMA, SFSCMA has excellent high temperature performance; compared with MA and SFMA, the low temperature performance of SFSCMA is improved, but it is worse than that of SBSMA. Moreover, when the temperature is lower than −30 °C, its low temperature performance is close to that of MA, or even worse than that of MA. After the compound modification of SF and SBSMA, the fatigue properties of the asphalt are improved, and the fatigue performance of SFSCMA is the best among the four kinds of asphalt. There is a cross-linking force in the network structure of SFSCMA, which restrains the flow of the whole system, so that the stability of the compound modified asphalt is significantly improved, which is favorable to the high temperature performance and fatigue resistance of the compound modified asphalt. However, due to its low mobility, it has a negative impact on the low temperature performance of the compound modified asphalt. In addition, according to previous studies, compared with diatomite, it is proven that SF can reach the same level as diatomite in improving the high temperature performance and fatigue performance of asphalt. Therefore, SF can be used as a good choice of asphalt modifier and can achieve the purpose of waste recycling and environmental protection.

In order to explore the influence mechanism of carbon nanotubes on the ultraviolet (UV) aging properties of the SBS-modified asphalt binder, the changes of functional groups in the one-dimensional infrared spectrum and two-dimensional infrared correlation spectrum are studied in this paper. The results show that the UV aging process of the SBS-modified asphalt binder is the process of alkane chain cleavage and reorganization, the formation of oxygen-containing functional groups and decomposition of SBS. The incorporation of carbon nanotubes can reduce the mutual conversion of methyl and methylene functional groups, inhibit the decomposition of butadiene and the destruction of C = C double bonds in SBS. The degradation of SBS during the process of UV aging leads to the change of many functional groups and acceleration of the aging of the SBS-modified asphalt binder. The addition of carbon nanotubes can effectively alleviate the degradation of SBS and the formation of oxygen-containing functional groups at the early stage of UV aging, and reduce the influence of these two changes on other functional groups; thus, improving the anti-aging performance of the SBS-modified asphalt binder.

In order to explore the diffusion and regeneration of bio-oil in aged bitumen, waste cooking oil (WCO), waste wood oil (WWO) and straw liquefied residue oil (SLRO) were selected in this paper. According to the surface wetting theory, the contact angle is obtained by combining laboratory experiments with molecular dynamics (MD) simulation, and the wetting parameters are calculated to evaluate the wetting behavior of bio-oil. The experimental phenomena of the wetting process and the main factors driving wetting are further analyzed. A permeation experiment is designed to obtain the permeation fusion layer (PFL). If the crossover modulus of PFLs changes compared with that of the aged bitumen, it is determined that the bio-oil penetrates the corresponding fusion layer. The results show that the motion of bio-oil included spreading and shrinking processes, and a precursor film played a pivotal role in the transportation of nanodroplets. Higher surface tension, lower viscosity and cohesion can effectively promote the wettability of bio-oil. A higher temperature and a longer permeation time are conducive to the permeation of bio-oil in aged bitumen. WCO with the strongest wettability has the weakest permeability, while WWO has superior permeability and can activate the macromolecules’ surface activity, but its wettability is relatively weak. It is necessary to further modify WCO and WWO to be suitable rejuvenators.

In order to study the characteristics and laws of nanocrack generation and self-healing behavior of asphalt materials under tensile action, the molecular dynamics (MD) method was used to simulate the continuous “tensile failure—self-healing” process, and this study remedies the shortcomings of existing experimental and observational methods. It is found that the MD-reproduced formation process of asphalt binder nanocrack contains four stages: “tensile extension”, “nanocrack generation”, “crack adding, expanding and penetrating” and “cracking failure”. The influence of tensile conditions on the tensile cracking simulation of an asphalt binder model was analyzed, and it was found that low temperature and high loading rate would increase the tensile strength of the asphalt binder model. In addition, the MD-reproduced healing process of asphalt binder nanocracks can be divided into four stages: “surface approach”, “surface rearrangement”, “surface wetting” and “diffusion”, which is similar to the healing process of polymers. Finally, from the perspective of energy change, the change rule of dominant van der Waals energy in the self-healing process was studied. Based on the existing research, the influence of damage degree on the healing performance of asphalt binder and its mechanism were further analyzed. The research results further enrich the theoretical research on microlevel cracking and healing of asphalt materials, and have certain theoretical value for the further development of self-healing asphalt materials.