Often the approach to restoration is to simply remove visibly deteriorated concrete while ignoring the fact that corrosion will continue within the surrounding concrete. However, the repaired areas will change from anodic to cathodic sites, thereby increasing the remaining cathode to anode ratio - this will increase the rate of corrosion of the remaining anodic sites. (as illustrated by the Figure) For this reason, I believe that the use of corrosion evaluation testing methods in conjunction with a delamination survey can be essential.
Experiences both in the laboratory and on restoration projects have convinced me that a very effective and economical way to achieve electrochemical compatibility is to apply a zinc rich epoxy primer to the exposed reinforcing steel within the repair area; the zinc acts as a sacrificial anode, thereby mitigating corrosion activity within the steel.
INVESTIGATING CONCRETE PROBLEMS
Learning from Those Who Learned the Hard Way!