Abstract
The cover zone in concrete strongly affects changes in the environment at the steel that can lead to corrosion initiation and propagation. Chloride binding by the cement in concrete may affect the rate of chloride ingress and chloride threshold level which in turn determine the time to chloride induced corrosion initiation. In this work an assessment of the influence of the cover zone in two common exposure environments is presented.
The application of electrochemical techniques for the control of corrosion on reinforced concrete structures, where the cover zone protection has been penetrated, is now well established. Electrochemical treatments applied to steel in concrete include cathodic protection and prevention, intermittent cathodic protection, chloride extraction and re-alkalisation. However these systems all demonstrate limitations related to complexity of operation which limits their application on site.
An analysis of available data on existing electrochemical treatments allows the development of a revised hypothesis on the relative importance of the protective effects of electrochemical treatments. This analysis indicates that electrochemical treatment processes designed to arrest corrosion of reinforcing steel can be improved. These improvements involve delivering an initial short term high current treatment to rapidly arrest the corrosion process minimising further corrosion induced damage and subsequently delivering a low current sustained treatment to ensure durability with low maintenance requirements.
