A PREDICTION METHOD FOR THE CHLORIDE DIFFUSIVITY IN PRESTRESSED CONCRETE CONTAINMENT VESSELS IN NUCLEAR POWER PLANTS

Chloride diffusivity is an important parameter for assessing the durability of prestressed concrete containment vessels in nuclear power plants located in a marine environment. Based on a two-scale method, a quantitative relationship between the capillary porosities of cement paste matrix and interfacial transition zone (ITZ), and the prestress is established by analyzing the mesostructures of cement paste matrix, ITZ and concrete under an equi-biaxial compression. To quantify the effect of prestress on the closure, initiation and extension of microcracks, an empirical formula between the critical capillary porosity and the prestress is proposed. Concrete is then modeled as a three-phase composite material, composed of aggregate, ITZ and cement paste matrix, and the chloride diffusivity ratio of concrete is obtained. Through comparison with experimental results, two parameters in the empirical formula are calibrated. The validity of the prediction method is preliminarily verified with three sets of experimental data.