Deterioration of fracture toughness of concrete under acid rain environment

Deterioration of fracture toughness of concrete caused by acid rain attack was investigated through laboratory-accelerated corrosion tests. Fracture toughness of the corroded concrete with different corrosion period was obtained by three point bending tests, and meanwhile the P-COMD curves and elastic modulus E of the corroded specimens with different corrosion degrees were also obtained. The experimental results showed that the deterioration of concrete surface is large and the corrosion depth increases with corrosion duration. The observation by scanning electron microscopy showed that the microstructures of crack tip are porous and loose due to acid corrosion, and many crisscross cracks appear at corrosion layer. Based on the experimental results, equivalent crack length in the fracture process zone and the effective fracture toughness KIC were also obtained by theoretical analysis. Under the impact of acid corrosion, the concrete material physical and chemical properties changed significantly, which made the corresponding resistance stresses to crack propagation decrease. The curves of fracture toughness versus corrosion depth were obtained in this study.