Determination of critical anodic and cathodic areas in corrosion processes of steel reinforcement in concrete

Abstract

Chloride-induced corrosion of steel reinforcement in concrete is one of the major reasons for deterioration of reinforced concrete (RC) structures. In the present paper the coupled 3D chemo-hygro-thermo-mechanical model for concrete is used to study the influence of the anode/cathode surface ratio on the corrosion rate and corrosion induced damage. It has been demonstrated that the position and size of anode and cathode strongly influences the crack pattern and the corrosion rate (Ožbolt et al., 2012, 2014). Currently there is no algorithm which can predict the combination between anode and cathode surfaces on reinforcement that results to the highest corrosion rate. Therefore, to investigate this influence the expression for maximum entropy production, deduced from irreversible thermodynamics, is formulated. The entropy is produced by dissipative processes, which are in this special case the flow of ions through the electrolyte, the anodic and cathodic polarization and the diffusion oxygen process. Through several numerical examples, in which the size and position of anodic and cathodic surfaces are varied, is demonstrated that maximum entropy leads to maximum corrosion rate.