REDUCTION OF CHLORIDE LEVEL IN REINFORCED-CONCRETE BY CATHODIC POLARIZATION TECHNIQUE

The premature deterioration of concrete structures after 5-10 years of service has become a major problem during the past few decades. The e conomic loss due to the corrosion of metals in concrete structures has been estimated at billions of dollars per year [1]. The role of chlor ide is very significant in the corrosion of reinforced concrete struct ures. This corrosion can be minimized by bringing down the chloride po llution level within the concrete. The tolerable limit of chloride var ies with the pH of concrete. Concrete with normal alkaline pH can tole rate up to 1000 ppm [2]. In this study, use of an electrochemical tech nique to remove or reduce the chloride content in reinforced concrete structures is discussed. Impressing current to increase the mobility o f chloride ions towards the solution on the surface from the inside of concrete can bring down the chloride contamination to well within the above limit. Different current densities for a period of 200 hours we re applied continuously and the critical current for maximum removal o f chloride has been identified. The change in the solution chemistry o f the electrolyte used for this purpose was monitored at an interval o f 25 hours. A rigorous analysis of the concrete in terms of pH and chl oride content was also carried out. Potentials of steel embedded in co ncrete were monitored before, during, and after polarization. Cathodic polarization technique was found to be useful for removal of chloride from concrete structures. A current density of 1 A/m(2) was found to be critical for maximum chloride removal.