Influencing Factors Of And Relationship Between Fatigue And Healing Properties Of Asphalt Binders

Fatigue cracking is one of the main distresses occurring in asphalt pavements,cracks normally occur in the interface between asphalt binders and aggregates or within asphalt binders,so investigation of resistance to fatigue cracking of asphalt binders is helpful to predict the fatigue life of asphalt pavements.The self-healing potential of asphalt binders reveals the necessity of considering the strength recovery from intermittent healing when charactering the fatigue performance of asphalt binders.Analyzing and comparing the existing evaluation methods of fatigue life,studying the influencing factors of fatigue performance,evaluating the self-healing capacity of asphalt binders and analyzing the factors which affect self-healing,establishing the relationship between self-healing properties and fatigue performance,are of great significance for the effective comparison of asphalt fatigue performance.The fatigue and self-healing tests were carried out by Dynamic Shearing Rheometer(DSR),The merit and weakness as well as the applicability of the evaluation methods for fatigue life were summarized.The fatigue life values of four asphalt binders calculated by different methods showed that the modulus-controlled method determined the minimum fatigue life value.The transformation relationship have been established between different fatigue life values using a fitting function,which was helpful to remedy the limitation of each evaluation method.The effect of stress levels,temperature,frequency and loading mode on fatigue performance were studied.With the increase of stress level,the fatigue life gradually decreased,and its variation law could be predicted by power function.The increase of temperature reduced the fatigue life of asphalt binders,while the increase of frequency increased the fatigue life of them.There were differences in fatigue damage development under controlled-stress and controlled-strain modes.The fatigue life under controlled-strain mode was higher than that of controlled-stress mode on the couple of equivalent loadings.The damage development could be divided into two stages based on the change of mechanical parameters: in the first stage,the fatigue development of the two models was consistent,in the second stage,the fatigue development was different,and with the increment of stress/strain level,the earlier the damage difference occurs.The cumulative dissipation energy of the two modes can be fitted by quadratic polynomial and there was a symmetric relation with respect to a straight line.A novel self-healing evaluation index that is more physical and more accurate was proposed in view of the deficiencies of the existing self-healing evaluation indexes.The macroscopic healing index corresponded to the theoretical healing index,and the static healing behavior equation was used for verification,which showed that the proposed method has better fitting goodness.The effect of intermittent time,damage degree and temperature on self-healing recovery was studied.With the increase of damage degree,the damage of asphalt was more severe and the recovery was worse.The growth of intermittent time could effectively improve healing,but this effect gradually faded with the increase of loading time.The increase of temperature improved the self-healing effect of asphalt binders,but the effect on different asphalt binders was different and not unrestricted.The significance of self-healing properties on fatigue property was analyzed.The correlation between healing characteristics and fatigue performance was summarized,and the self-healing recovery and self-healing rate were differentiated.The self-healing recovery of asphalt binders was converted into the increased fatigue life and a method was put forward of comparing the fatigue performance under a single interval.According to the relationship between the increased fatigue life,damage degree and interval time,the formulation for calculating the true fatigue life of asphalt binders under repetitive and intermittent loading was established,which had more realistic prediction of the service life of asphalt pavements.