Tensile Fracture Characteristics and Dynamic Crack Evolution Law of Concrete

To investigate the tensile fracture characteristics and crack evolution mechanisms of concrete, Brazilian disc quasi-static splitting tests and falling weight impact tests were conducted. The crack propagation and mechanical responses were analyzed using the finite cohesive-element method (FCEM). Test results demonstrated that under quasi-static loading, concrete discs exhibited tensile fracture with a primary crack penetrating along the loading direction at the disc center, accompanied by minor parallel secondary cracks. Crack propagation primarily occurred within the mortar matrix and along aggregate-mortar interfaces. The tensile performance of three-dimensional concrete discs exhibited significant enhancement with increasing thickness-diameter ratio. Under dynamic impact loading, specimens maintained a center-initiated fracture pattern, where the main crack propagated along the loading diameter, while triangular crushing zones formed at the edges in contact with testing apparatus. With increasing drop height, the specimens sequentially exhibited four distinct failure modes: no crack initiation, crack initiation without penetration, complete crack penetration, and severe fragmentation. High-speed photography quantified time-dependent crack lengths, demonstrating prolonged crack propagation durations at reduced drop heights. Numerical simulations revealed a nonlinear decreasing trend in crack initiation time versus drop height, with an empirical formula established to describe their relationship.