Revisiting Surface Resistivity as a Predictor of Corrosion Rates in Reinforced Concrete

ABSTRACT The corrosion of reinforcing steel poses significant challenges to the integrity and economic viability of concrete structures, threatening their safety and durability. To approach the study of their corrosion behavior, we propose herein a time‐extended version of the R‐C model, allowing us to revisit the role of conductivity as a predictor of corrosion rate. We have fabricated four concrete slabs submitted to an accelerated corrosion process over 90 days, exposed to a 5% NaCl solution and to a controlled current density of 100 µA/cm 2 . We have hence proposed a multivariate analysis to correlate the rate of corrosion, concrete resistivity and time, permitting us to resolve the specific contribution of chloride uptake and the calcium silicate hydrate (C‐S‐H) matrix, as opposed to applied current to the steel rebar. The corrosion process was further investigated using electrochemical impedance spectroscopy (EIS) to determine the complex interactions at the concrete‐reinforcing steel interface. We further identified the chemical nature of the corrosion products, where the formation of akaganeite and tilleyite was confirmed, thus establishing the interplay between chloride‐induced corrosion and the modification of the concrete matrix.