Critical chloride threshold values as a function of cement type and steel surface condition

This paper presents the application of a new test protocol developed for determining chloride threshold values initiating corrosion in reinforced concrete. The experimental set-up was described in previous work and is based on the intrinsic localized aspect of chloride-induced corrosion. The test protocol is also based on the concept of anodic control of corrosion initiation, and therefore independent of the area of passive steel. The test method is applied to mortar and concrete formulations with different binders and steel surface conditions. Chloride-binding isotherms were also determined to allow the transition from total to free chlorides. It is found that the test protocol is rapid and applicable to all formulations. The experimental results provide an understanding of the influence of binder type, w/b ratio and porosity on chloride-induced corrosion initiation. As expected, the steel surface condition is shown to have an important overall effect on corrosion initiation.