Identifying Fatigue Crack Initiation and Propagation Behavior of Asphalt Binder Under Dynamic Shear

Fatigue cracking caused by repeated load is one of the main distresses of asphalt pavement diseases. In recent years, the fatigue performance of asphalt binder can be evaluated and distinguished by the damage mechanics approach based on time sweep (TS) and linear amplitude sweep (LAS) tests; however, the cracking development process cannot be captured and clarified. In this paper, fracture mechanics-based approach is proposed to address the problem that the damage characteristics of different asphalt fatigue phases can not be accurately characterized by existing asphalt fatigue modelling method, which reveals the specific phases during the fatigue process. The crack growth curve is proposed to identify the crack initiation and propagation behavior in the TS test, whereas in LAS test the crack propagation characteristic curve should be effectively utilized for such purpose. The energy release rate can be utilized as the unified failure identification for both LAS and TS tests. Additionally, both LAS and TS tests demonstrate that the fatigue resistance of asphalt binder is primarily determined by its crack propagation life. The addition of SBS modifier can both effectively improve the crack initiation life and crack propagation life.