Assessment of corrosion attack morphology on reinforced concrete structures exposed to chlorides

Chloride-induced corrosion of the reinforcement steel is the main degradation mechanism for reinforced concrete, considerably affecting the load and deformation capacity of structures. Despite its importance, there is limited knowledge about the morphology of corrosion attacks and accordingly, relatively crude assumptions are generally made when considering corrosion in structural analyses. Improved understanding could reduce maintenance costs and extend the service life of structures. This study presents a systematic documentation and analysis of more than 600 corrosion attack morphologies, both from observations on actual engineering structures and from laboratory specimens (X-ray computed tomography data from previous studies). Findings reveal that corrosion attacks - regardless of age, concrete type, or whether occurring in structures or laboratory specimens - without exception grow laterally and longitudinally along the reinforcement bar, rather than in depth. This shallow morphology deviates from the conventional description of pitting corrosion in the literature. Therefore, we propose using the term ‘corrosion attack’ instead of ‘corrosion pit’ for better differentiation. We discuss different mechanism that may lead to this growth pattern. Moreover, implications for the consideration of corrosion in structural analysis are assessed. A comprehensive database of the documented corrosion attacks is provided to enhance existing service life models, offering substantial data for probabilistic modeling of input parameters.