Cross-Scale Characterization of Fatigue Damage in Warm-Mix Asphalt Based on Linear Amplitude Sweep and Four-Point Bending Tests.

Fatigue cracking is a critical factor governing the long-term durability of asphalt pavements, while the cross-scale relationship between binder fatigue behavior and mixture fatigue performance remains insufficiently understood for warm-mix asphalt (WMA). In this study, the fatigue characteristics of WMA were systematically investigated at both binder and mixture scales to establish quantitative cross-scale correlations. Dynamic shear rheometer (DSR) tests and linear amplitude sweep (LAS) tests interpreted using the simplified viscoelastic continuum damage (S-VECD) framework were employed to characterize the rheological properties and damage evolution of asphalt binders with different crude oil origins. Mixture-scale fatigue performance was evaluated using strain-controlled four-point bending fatigue tests. The results indicate that aging significantly increases binder stiffness and accelerates fatigue degradation, with the fatigue factor G*·sin δ increasing by approximately 150-250% after long-term aging. The effectiveness of warm-mix modification at the binder scale was strongly binder-dependent, as reflected by an 8-13% reduction in the damage rate coefficient for Binders A and B but an approximately 11% increase for Binder C. Conventional rheological indicators such as sin δ exhibited limited and material-dependent capability in predicting mixture fatigue life, whereas LAS-S-VECD-derived damage parameters showed consistently strong correlations with mixture-scale fatigue performance. Overall, this study demonstrates that LAS-S-VECD-based binder damage characterization provides a robust basis for predicting mixture fatigue resistance and supports its application in performance-based mixture design for durable and sustainable WMA pavements.