Multiscale Correlation of Fracture Surface Morphology and Low‐Temperature Mechanical Performance in Asphalt Mixtures

To elucidate low‐temperature cracking mechanisms in asphalt mixtures, this study integrated direct tensile fracture testing with 2D image analysis and 3D laser scanning, linking macroscopic mechanical behavior to microscopic morphology. Results indicate that crack resistance is governed by structural synergy between a coarse aggregate skeleton and ductile modified asphalt. This synergy increases macroscopic fracture process energy during low‐temperature crack propagation. Notably, quantitative analysis of mix designs reveals an optimal filler–binder ratio of 1.2 (F/B = 1.2) for maximizing fracture resistance. Based on surface energy theory, dual‐dimensional analysis reveals the underlying mechanism: The synergistic effect increases spatial surface tortuosity and reduces brittle interfacial failure. Consequently, cracks propagate along intricate paths requiring greater external mechanical work. Furthermore, a comprehensive morphological index was established using principal component analysis. Serving as a thermodynamic indicator of fracture paths, this index provides a quantitative framework for evaluating macroscopic low‐temperature stability beyond mere statistical correlation.