Fracture behavior and deterioration mechanisms of hydraulic concrete under wet-dry cycles with variable temperature

• Analyze the degradation of concrete fracture properties . • Analyze the process and mechanism of concrete crack extension. • Determination of concrete fracture mode conversion based on AF-RA data. • Analysis of temporal and spatial fracture parameter differences using multiple fractal theory. Photovoltaic pumped storage power plants, as a kind of green low-carbon, flexible and adjustable power source with potential for large-scale development, are often affected by environmental factors such as variable temperature and wet/dry cycling during operation, which leads to the degradation of the mechanical properties of the panels and thus affects the structural stability. In this study, wet and dry cyclic concrete specimens were prepared by simulating a 12-hour cycle of high temperature drop (80 °C → 20 °C) conditions in a homemade test chamber. The damage mechanism of the fracture resistance of deteriorated concrete and the crack extension process were investigated by using three-point bending test combined with acoustic emission multiparameter monitoring technique. The experimental results show that the fracture instability load of the deteriorated material decreases gradually and the double-k fracture parameters change significantly; the average crack initiation toughness decreases by 44.02 % and the average instability toughness decreases by 20.39 %. The proportion of shear components in the fracture process increased from 17.1 % to 26.6 % with the increase in the number of cycles. The crack extension path shows a shift from aggregate penetration to interface bypassing, and exhibits random extension of microcracks, spatial non-homogeneity, and local energy aggregation effect triggered by the synergistic effect of multiple factors. This study provides a theoretical basis for the stability of concrete structures in pumped storage power stations.