Multi-Scale Mechanisms of Polyphenol-Grafted Submicron Mineral Fillers Regulating Fracture Resistance of Asphalt Mixtures across Oxidative Aging States

Oxidative aging stiffens asphalt mixtures and accelerates cracking, and aging-induced polarity shifts weaken the asphalt-mineral interface. This study grafts submicron basalt fillers with catechol or gallic acid and incorporates them into asphalt mixtures to regulate aging-related damage. Fracture is evaluated by semi-circular bending with simultaneous acoustic emission (AE) and digital image correlation. RA and AF features are extracted from AE; a Gaussian mixture model in RA-AF space identifies tensile, shear, and boundary events using posterior probability ≥ 0.60, avoiding empirical divider lines. Lower temperature and greater aging shift the response toward brittleness, with higher peak load, reduced peak displacement, and steeper post-peak softening. Polyphenol-grafted fillers moderate the post-peak drop and reduce high-amplitude bursts, indicating more gradual damage accumulation. Across all conditions, tensile events dominate (51.2%-86.4%), shear events are secondary (11.5%-43.4%), and boundary events rise to ∼31% in specific temperature-aging combinations. Molecular dynamics simulations show pronounced interfacial segregation of asphalt fractions (relative peaks ∼4-7 near the mineral surface); gallic-acid functionalization yields smoother, more consistent profiles across aging states, implying improved microstructural stability. Overall, polyphenol-grafted submicron fillers—especially gallic acid—mitigate aging-related cracking by stabilizing interfacial organization and reshaping the fracture damage sequence.