Morphological characteristics of crack branching in asphalt mixtures under compression

Abstract

Crack branching is a multi-crack propagation problem. Singular crack tip elements are frequently encountered, and defining the multi-crack tips’ enrichment functions is difficult. To overcome these drawbacks, this study used an already developed ordinary state-based peridynamics method to simulate crack branching in AC-13, AC-20, and PAC-13 asphalt mixtures. These asphalt mixtures’ digital images were acquired by an X-ray computed tomography method. Next, the Prony series coefficients of the fine asphalt mixtures were obtained by the dynamic modulus test. After that, the fracture energy of the fine asphalt mixtures was measured by the semi-circular bending test. Finally, the measured asphalt mixture properties were input into the ordinary state-based peridynamics method in order to simulate crack branching in the AC-13, AC-20, and PAC-13 asphalt mixtures. The simulation results indicate that the diagonal crack first emanates in asphalt mixtures. Then, the diagonal crack continues to branch into a wing crack, splitting crack, and branched crack. These four types of cracks can generate eight crack branching categories in asphalt mixtures. The crack branching trajectory was quantified by the fractal dimension, whose value ranged from 1.14 to 1.64. The physical significance of the fractal dimension explains the changes of crack branching paths in the asphalt mixtures.