Experimental Study and Prediction of Strength and Stiffness Degradation of Boric-Acid-Corroded Concrete

Durability tests were performed on concrete representative of nuclear power plant structures exposed to boric acid leakage. Boric acid is widely used in pressurized water reactor systems for neutron absorption and chemical control; therefore, accidental leakage or evaporation-induced concentration of borated water can create an important durability concern for adjacent concrete structures. Three boric acid concentrations (0, 2500 and 18,000 ppm) and two temperature levels (20 and 60 °C) were considered. The evolution of cube compressive strength and elastic modulus with exposure age was examined over 180 days. The results show a slight increase in concrete strength and stiffness during the early stage of exposure, followed by a continuous increase in the loss ratios of cube compressive strength and elastic modulus at later ages. The maximum measured strength–loss ratio was 4.684%, and the maximum measured elastic modulus–loss ratio was 1.755%. A service life prediction model based on loss ratio parameters was then developed from the test results. The fitted examples gave high coefficients of determination (R2 = 0.9960 for cube compressive strength and R2 = 0.9947 for elastic modulus), indicating that the proposed model can support durability assessment and aging management of boric-acid-corroded concrete structures in nuclear power plants.