The influence of cracks on the corrosion initiation time caused by chloride diffusion in concrete structures using the Boundary Element Method

Abstract

Reinforced concrete structures in coastal zones are subject to corrosion triggered by chloride ions. In contact with the concrete surface, such ions penetrate through the material’s porous microstructure, mainly by diffusion, and accumulate on the reinforcement’s surface, promoting a local breakage of the passive layer. In the classic structural service life model, the time span between the structure’s exposure to chloride ions and the reinforcement depassivation is called corrosion initiation time, which may be drastically reduced in cracked concrete. Aiming to estimate the corrosion initiation time, this study uses the two-dimensional transient formulation of the Boundary Element Method (BEM) to model the chloride diffusion in reinforced concrete parts with pre-existing cracks. In this approach, different crack lengths are simulated using the subregion technique, whose crack thickness is not required. The reinforcements are represented by circular voids with nil flux in the boundary. In a rectangular beam cross-section, cracks up to 60 mm long were simulated from the concrete cover. Based on the cases studied, the influence of concrete cracking on corrosion initiation time is more significant for cracks over 20 mm long, although this result may vary depending on the position of the crack relative to the reinforcement.