Interfacial Dynamic Fracture Behavior and Crack Evolution in Phosphogypsum‐Based Concrete–Rock Composites

ABSTRACT To address phosphogypsum stockpiling pollution, this study investigates the dynamic fracture behavior of phosphogypsum‐based concrete‐rock (PC‐R) composites using PFC2D simulations. Simulated dynamic three‐point bending tests on notched semi‐circular bend (NSCB) specimens reveal that a 25% phosphogypsum aggregate (PA) content marginally reduces interfacial fracture toughness ( K IC ) by 5.89%–8.33% due to mechanical interlocking and internal curing effects. However, as PA increases, fractures divert into the concrete matrix, with 100% PA causing a 32.40%–39.85% K IC drop. Consequently, crack propagation shifts from a singular interfacial path to a dual interface‐matrix mechanism. The dynamic K IC exhibits strong loading‐rate sensitivity, accurately captured by a mixed exponential model. Additionally, the fracture process zone (FPZ) length increases nonlinearly; exceeding a 75% PA threshold forms extensive internal pore networks, triggering a macroscopic brittle‐to‐ductile transition. These findings provide theoretical foundations for composite structural design and promote sustainable phosphogypsum utilization.