Sensitivity of chloride-induced corrosion rate of steel in concrete to cover depth, crack width and concrete quality

Abstract

This paper presents the results of analyses carried out to assess the sensitivity of chloride-induced corrosion rate to change(s) in cover depth, concrete quality and crack width. An empirical chloride-induced corrosion rate prediction model is used to carry out the sensitivity analyses. The main model input parameters for the model are surface crack width (w cr), cover (c) and concrete quality (characterized by a long-term diffusion coefficient, D 90). A two tier sensitivity analysis is carried out to establish (i) which individual input parameter (D 90, c or w cr) corrosion rate is most sensitive to, and (ii) which combination of two input parameters out of the possible three (D 90, c and w cr) corrosion rate is most sensitive to. The sensitivity analyses results show that in cracked concrete change in corrosion rate is greater if concrete quality is varied than if either crack width or cover depth is varied i.e. concrete quality has a dominating role on the effect of either crack width or cover depth on corrosion rate. Generally, in cracked concrete corrosion rate is more sensitive to change in concrete quality than change in either crack width or cover depth. Even though cover cracking increases corrosion rate, and that it should be minimized, a holistic approach considering the effect of cover depth, crack width, and more importantly, concrete quality on corrosion rate should be adopted.