CRITICAL CHARACTERIZATION OF CRACK INITIATION AND UNSTABLE PROPAGATION FOR EPOXY ASPHALT CONCRETE

In order to determine the critical points of the crack initiation and unstable propagation for epoxy asphalt concrete (EAC), firstly, a three-dimensional (3D) virtual specimen of EAC with heterogeneous (coarse aggregates, asphalt mastic and air voids) and multilayer (aggregate gradation) morphological features was reconstructed. Secondly, the virtual three-point bending test of a single-edge notched beam was implemented using the discrete element method (DEM), and a digital camera method was used to capture the surface crack development of the experimental beam specimen. Finally, the changing relationship between the crack tip opening displacement (CTOD) and the crack mouth opening displacement (CMOD) throughout the crack development was analyzed. The results indicate that the introduction of δ₂₅ representing CTOD provides a new idea for understanding the energy occurring in the fracture zone used for crack propagating. Additionally, the two governing points on the relationship curve between CTOD and CMOD approximately describe the initiation and critical unstable propagation of cracks, respectively. Meanwhile, the crack development of EAC includes three stages, namely, initiation, stable and unstable propagation. Furthermore, it is found that the analysis method based on the δ₂₅-CMOD curve can be used as a supplemental tool to investigate the fracture behavior of EAC.