Modeling the Corrosion Rate of Steel Reinforcement in FRP-Wrapped Concrete

A model to predict the corrosion rate of steel reinforcing bars in fiber-reinforced polymer (FRP) wrapped concrete columns is presented. A model proposed by the author to predict the reinforcement corrosion rate and cracking of the concrete cover due to diffusion of chloride ions and oxygen in concrete members is modified to predict the corrosion rate of reinforcing bars inside FRP-wrapped columns. As corrosion progresses and rust layers build up, oxygen has to diffuse through three different layers to be consumed in the cathodic reaction: the FRP wrap, the concrete cover, and the rust layer. As the rust layer thickness increases, the corrosion rate decreases until it reaches a very slow steady-state descent. The predicted corrosion rate is compared with experimental results reported in the literature. Initially, the model proposed previously by the author was used to predict the corrosion rate of an unwrapped pile to calibrate parameters such as the diffusion coefficient of oxygen with experimental data reported in the literature. Subsequently, the modified model was used to predict the corrosion rate of reinforcing steel in an FRP-wrapped column. The model yields very good agreement with experimental results reported in the literature.