Acidification induced deterioration of concrete cathodic protection systems and its management

Oxidation of water can occur at concrete cathodic protection (CP) system anode surfaces resulting in the production of hydrogen ions and consequent generation of acid. If chloride ions are present then oxidation of chloride ions to hypochlorous acid and hydrochloric acid can also occur. Such acid generation at anode surfaces has been known for nearly 200 years for metallic CP. Acidification induced deterioration of reinforced concrete structures to which CP has been installed has occurred in Australia. Oxidation reactions at anode surfaces generating acid has led to the deterioration of the cementitious grout and concrete around anodes in various bridge and wharf reinforced concrete structures. The accelerated deterioration is attributed to design, installation and operation errors, but most particularly improper design. Lessons learnt from such field examples are outlined. Concern is expressed that excessive anode material of too high a surface area is being designed for some systems and the consequential performance expectations of the grouts is then unreasonable. There have been recent new technologies or technological changes in anodes and grouts and these are also mentioned as they are of relevance to the design of concrete CP systems as well as the engineering of the management of acidification induced deterioration of concrete CP systems for structure owners. Management of the acidification induced deterioration has not been possible with some existing bridge concrete CP systems as the opportunity for maintenance and rectification had passed. However, with other systems a management plan has been engineered that has led to the ongoing successful protective performance of the systems with affordable ongoing maintenance costs to the structure owners and implementation by structure owner resources and not specialist CP suppliers or CP contractors.