Using X-ray microtomography to study the initiation of chloride-induced reinforcement corrosion in cracked concrete

Abstract

Corrosion is the main cause of premature degradation of reinforced concrete structures. In particular, the mechanisms of chloride-induced corrosion in cracked structures are not fully elucidated. The aim of this study is to investigate by X-ray tomographic imaging the initiation and propagation of chloride-induced corrosion in cracked concrete. On reinforced prismatic cracked specimens exposed to seawater spray-drying cycles, the approach consists in characterizing in a non-destructive way the crack geometry, corroded steel volume and corrosion products migrating in the cementitious matrix and crack, as a function of time. Sub-volume scans and difference images allow a study of the first stage of chloride-induced corrosion in cracked concrete with respect to the number of spraying cycles, geometry and crack opening. The volume of steel consumed measured by 3D imaging is validated against destructive measurements, and it is shown that insights about the phenomenology of pitting (depth, displacement of corrosion products, densification, crack clogging…) can be obtained.