Fatigue-induced degradation of self-healing properties of asphalt mixtures: Mechanisms and quantitative characterization

Understanding how self-healing properties degrade during fatigue processes is crucial for improving the accuracy of fatigue life predictions in asphalt mixtures. This study refined the indirect tensile (IDT) fatigue test method and introduced a novel self-healing parameter E(n)_Healing,F-H, derived from elastic modulus variations. The validity of the IDT fatigue-healing test was confirmed, and the effects of binder type, loading mode, and freeze-thaw cycles on E(n)_Healing,F-H were systematically investigated. Results demonstrated that the IDT fatigue-healing test effectively quantified self-healing properties, revealing significantly extended fatigue life compared to conventional IDT fatigue tests. The E(n)_Healing,F-H captured an exponential degradation of self-healing properties with accumulated fatigue damage. Notably, under high stress ratios, low frequencies, and multiple freeze-thaw cycles, E(n)_Healing,F-H exhibited nearly linear and accelerated degradation with increasing fatigue cycles. However, extended load intervals and higher frequencies alleviated E(n)_Healing,F-H degradation, whereas increased stress ratios and freeze-thaw cycles amplified it. To enhance the predictive accuracy of crack resistance performance, the E(n)_Healing,F-H was integrated into the HMA-FM (Hot Mix Asphalt Fracture Mechanics) self-healing model. This integration corrected the overestimation of healing effects and provided a more comprehensive healing model.