Mechanism Analysis Of The Differences Of Asphalt Fatigue Damage Under Stress And Strain Control Mode

The fatigue damage characteristics of asphalt and asphalt mixture have beenpaying much concern and attention by researchers. Aspalt fatigue tests are conductedunder control stress mode and control strain mode, however, almost all studies haveshown that the fatigue properties of asphalt under these two control modes aresignificantly different. This differences make it difficult to determine evaluation indexof asphalt fatigue properteis, which leads to difficulty to compare fatigue resistanceperformance of asphalt and choose quality asphalt for asphalt pavement construction.On the other hand, although in recent years some researchers have noticed the problemsand confusions caused by asphalt fatigue difference under different control mode andincreased emphasis on research in this area, most studies focuses on asphalt mixture andthe unity of phenomenon and there are no fundamental analysis on mechanism ofasphalt fatigue difference under control stress mode and control strain mode. Therefore,it is necessary to research on the mechanism of asphalt fatigue differences underdifferent control mode and built a unified evaluation index of asphalt fatigue.Taking these issues into account, firstly, the deformation characteristics of asphaltunder static and dynamic loades were studied in this paper. On this basis, withcomparing and analyzing the existing asphalt constitutive equation, the constitutivemodel which can reflect the deformation characteristics of asphalt more accurately wasselected, which provided the basis to the following establishment of asphalt fatiguedamage evolution model.Secondly, based on fatigue tests under different control modes, temperatures andloads, changing law of complex modulus, phase angle, dissipated energy, accumulateddissipated energy and so on under different control modes in fatigue processing wereanalyzed, and the differences of asphalt fatigue properties under different control modeswere studied, thus, the effect phase and control mode effect threshold were determined.Finally, based on the differences of asphalt deformation properties under differentcontrol modes, the changes of different viscoelastic parameters during fatigueprocessing were further analyzed, and the fatigue characteristics of asphalt and themechanism of asphalt fatigue damage differences under control stress mode and controlstrain mode were described. On this basis, combined with asphalt constitutive model,the damage evalution model of asphalt fatigue and the conversion function of asphatfatigue damage properties under stress control mode and strain control mode wereestablished.This study reveals the essence of asphalt fatigue, and have great significance forasphalt fatigue performance evaluation and prediction. In addition, the research findings have some reference value for analysis of damage mechanism of other viscoelasticmaterials, and the development of pavement mechnics and materials science.