Modelling steel corrosion in concrete structures

A comprehensive finite element model for predicting the rate of steel corrosion in concrete structures is developed. The model consists of initiation and propagation stages which are cast in the same time and space domains; i.e., processes which commence in the initiation stage, such as temperature, moisture, chloride ion, and oxygen transport within concrete, continue in the propagation stage while active corrosion occurs contemporaneously. This allows the model to include the effects of changes in exposure conditions during the propagation stage on corrosion and the effects of the corrosion reactions on the properties of concrete. The corrosion rates on steel surface are calculated by solving the Laplace's equation for electrochemical potential with appropriate boundary conditions. These boundary conditions include the relationship between overpotential and current density for the anodic and cathodic regions. Due to the non-linear nature of these boundary conditions, a non-linear solution algorithm is used. The developed model will enable designers to carry out comprehensive sensitivity analyses and to gauge the significance of variations in the values of certain parameters on the rate of corrosion in concrete structures.