Fatigue Damage Evolution Mechanism of Asphalt Binder Under Variable Stress Repeated Loading.

Continuous loading on asphalt pavements induces fatigue damage at the interface between the asphalt binder and aggregate or within the binder itself. The understanding of asphalt's fatigue response is considered crucial for the prolongation of pavement service life. Variable stress fatigue tests were conducted on asphalt binders, with conditions such as stress amplitude being altered to analyze fatigue performance and life. This study refines asphalt fatigue evaluation systems, introducing a variable stress time sweep test. Modulus recovery after stress changes was revealed through rheological analysis, indicating damage recovery. Fracture surface analysis showed that increased high-stress loadings resulted in reduced edge flow zone width and a flatter surface. Statistical analysis indicated an "exercise effect", enhancing fatigue life in the second stage. Stress transitions altered fatigue crack paths, surpassing Miner's linear criterion prediction. The fatigue life curve was accurately fitted using the two-stage life model, affirming its applicability in evaluating variable stress fatigue tests.