Analysis of Chloride Penetration in Concrete

Abstract

Reinforced concrete structures exposed to aggressive environmental conditions often exhibit damage caused by chloride-induced corrosion of reinforcement. The damage occurs in the form of cracking and spalling of the concrete cover due to the expansion of corrosion products, which adversely affects the bearing capacity and durability of structures. Moreover, the cross-sectional area of reinforcement decreases simultaneously with concrete deterioration. However, the damage occurs shortly after steel depassivation caused by critical chloride concentration in the vicinity of the reinforcement. The time necessary for critical chloride concentration to reach the reinforcement is called initiation phase and the main objective of this paper is to estimate its duration. The duration of the initiation phase is possible to predict if transport processes, which take place through the concrete cover, are accounted for. The most important physical processes related to steel depassivation are the transport of capillary water, chloride and heat. Therefore, the development of a 2D is presented in this paper. The model is based on the finite difference method and simulates aforementioned transport processes. The application of the model is shown on a numerical example in which a square cross-section of a reinforced concrete column is exposed to aggressive maritime conditions. The analysis is carried out to investigate the influence of crack width in concrete cover on the duration of the initiation phase. The numerical results show that the cracking of concrete cover significantly reduces the duration of the initiation phase, and, consequently, the service life of structures.