Relationship of electrical resistivity and corrosion rate in alkali-activated mortars with varying alkalinity and nitrite inhibitor

Abstract

The quantitative relationship between electrical resistivity and corrosion rate of steel (noted as R-C relationships) is empirical but informative in indicating corrosion risk of reinforced concrete in complex environments. However, it remains unclear how the R-C relationship line is affected by the chemistry and microstructure of cementitious binders. In this work, the corrosion behaviors of steel embedded in alkali-activated slag (AAS) mortars with varying alkali dosages were investigated to uncover the role of hydroxide ion concentration (pH) of pore solution in R-C relationship lines. Additionally, the effectiveness of sodium nitrite as a corrosion inhibitor in AAS was evaluated under high pH and chloride-rich conditions, as well as its effect on the R-C relationships. The results show that the intercept of R-C relationship lines increases with the decrease of alkali dosage in activators, which is mainly attributed to the pH drop in cementitious materials. Moreover, the slope of R-C relationship lines is a parameter related to pore structure and has a linear correlation with the average pore diameter measured by mercury intrusion porosimetry. Additionally, the efficacy of sodium nitrite as a corrosion inhibitor in AAS is insignificant, likely due to its detrimental effect on pore structure and enhanced water absorption.