Molecular Dynamics Simulation Of Self-healing Behavior Of Asphalt Materials

Since the reform and opening up,China’s highway construction has made great achievements,but the problems related to the self-healing of asphalt mixtures have not yet been fundamentally resolved.The selfhealing behavior of asphalt mixture refers to the process in which micro-cracks appear when the pavement is subjected to repeated loads.When the load disappears,the micro-cracks in the asphalt mixture are healed and the performance of the pavement is gradually restored.Asphalt self-healing ability is the core influencing factor of pavement self-healing.The research on self-healing technology of asphalt and asphalt mixture has important practical significance for the sustainable development of road materials.The main research contents and results are as follows:1.Use the four-component method to establish a molecular model of asphalt.Through density comparison,asphalt molecular radial distribution function analysis,solubility parameter and cohesive energy density calculation,and glass transition temperature comparison,the rationality of the asphalt molecular model is verified,and the glass transition temperature is compared from simulation and experiment measurements.It is concluded that the SBS modifier can improve the low-temperature working performance of the base asphalt,and the aging of the asphalt will cause the asphalt to enter the glass state in advance,making the low-temperature working performance of the asphalt worse.2.Through the self-healing simulation of the three asphalts of base asphalt,SBS modified asphalt and long-term aging asphalt at different temperatures,it is concluded from the analysis of diffusion coefficient,activation energy and frequency factor that the three asphalt self-healing occurs the degree of difficulty of time,the speed of healing in the process of self-healing,and the instantaneous strength formed during self-healing.Among the three asphalts,matrix asphalt is the most prone to self-healing process,SBS modified asphalt is the most difficult to self-heal process.In terms of the formed instantaneous strength,the instantaneous strength formed by selfhealing of SBS modified asphalt is significantly higher than that of the other two asphalts,and the self-healing instantaneous strength of long-term aging asphalt is the lowest.In terms of healing speed,SBS modified asphalt has the fastest self-healing speed,and with the increase of temperature,the rate increases the fastest.The healing speed of base asphalt and long-term aging asphalt is not much different,and the healing speed of long-term aging asphalt is the fastest.Based on the analysis of the three indicators,the self-healing ability of the three asphalts has been significantly enhanced with the increase of temperature.Among them,the self-healing performance of SBS modified asphalt is the best,and the self-healing ability increases with the increase of temperature.The fastest is the base asphalt,and the long-term aging asphalt has the smallest increase.3.In order to explore the effect mechanism of SBS modifier and long-term aging on the self-healing ability of matrix asphalt,analyze the self-healing process of SBS modified asphalt model,long-term aging asphalt model and matrix asphalt model at 80℃,and found: SBS The modifier increases the overall self-healing ability of the asphalt by changing the diffusion coefficient of the oil in the base asphalt.Due to oil volatilization and oxidation of long-term aging asphalt,the dispersant in the asphalt decreases,and the dispersant increases,so the overall self-healing ability of the asphalt weakens.4.By comparing the adhesive self-healing and adhesive self-healing at different temperatures,the relationship between the adhesive energy and the adhesive energy is analyzed,and it is found that the adhesion damage is more likely to occur in the microscopic state,and the adhesion is relatively firm.And in the case of low and medium temperature,the adhesive self-healing ability is strong;under the high temperature,the adhesive self-healing ability is strong.5.Comparing the data obtained from the fatigue-healing-fatigue test using DSR with the molecular simulation results,it is found that the molecular dynamics simulation of the self-healing process of asphalt is accurate,and the self-healing process of both the simulation and the test is consistent with Arrhenius law.The test self-healing index HI and molecular simulation of the diffusion coefficient in the self-healing process are curve-fitted according to the Arrhenius law,and two important parameters in the asphalt selfhealing process are obtained: activation energy and frequency factor.The parameters and diffusion coefficient can be used to predict the self-healing ability of asphalt.Both the test and simulation results show that the self-healing ability of SBS modified asphalt is stronger than that of base asphalt,and as the temperature increases,the healing ability of the two gradually increases.