Reinforcement corrosion is the most significant durability problem affecting New Zealand concrete bridges. Cathodic protection (CP), chloride extraction and realkalisation are electrochemical treatments that are designed to prevent further deterioration for considerably longer than the typical 10-year repair cycle offered by traditional patch repair techniques. They do not require extensive removal of contaminated but sound concrete.
To inform New Zealand bridge asset managers about the potential benefits of these techniques, their technical features are summarised and opportunities and limitations for their use on New Zealand bridges are identified in this report, prepared in 2001-2002. Case studies of overseas applications similar to possible New Zealand bridge applications are presented, and Australian designers and suppliers of treatments are listed. These data were current to July 2002.
Evaluation of data from the case studies and from a literature review suggests that CP offers protection for the remaining life of a structure, although it must be continuously monitored and maintained throughout that time. It is suggested as suitable for structures affected by chloride-induced contamination. Chloride extraction was considered to offer up to 20 to 30 years of protection, and is suggested as suitable for concrete exposed to atmospheric chloride contamination. Realkalisation was considered to offer permanent protection from carbonation-induced corrosion, although this is not a major problem on New Zealand bridges.
Keywords: Bridges, cathodic protection, chloride extraction, concrete, concrete repair, corrosion, extrochemical treatments, New Zealand, realkalisation, reinforcement