Electrochemical-Mechanistic Model for Concrete Cover Cracking Due to Corrosion Initiated by Chloride Diffusion

Abstract

A holistic electrochemical-mechanistic model of the corrosion of steel reinforcing bars inside concrete that accounts for the diffusion of oxygen and moisture into the concrete and rust layers, the densification of rust due to confinement, the flow of rust into the concrete pores, the development of internal pressure due to rust buildup, and cracking of the concrete cover is presented. The relationship between the corrosion current and the pressure buildup due to the corrosion products for different concrete cover thicknesses and concrete quality was calibrated through experiments using an accelerated corrosion test with an applied current. Results from finite-element analysis with an inelastic smeared crack concrete model were used to calibrate a simple analytical model of the critical internal pressure required to cause cracking of the concrete cover. The various submodels are linked together to predict the time for cracking of the concrete cover from the time of corrosion initiation. Results of parametric studies using the model indicate that the main factors that control the corrosion current and the time to cracking are the boundary condition, water-cement ratio, and concrete cover.