Abstract
An experimental study was carried out to find out the threshold value of chloride ion and hydroxy ion ratio (=[Cl ]/[OH]: mol ratio) for the onset of reinforcing steel corrosion in concrete. After the application of electrochemical method (desalination and realkalization), a five-year follow-up survey on the specimens was carried out in order to check the performance of the rehabilitation method.
The experimental results showed that when the pH value was 12 or more and Cl/OH ratio was 1 or less, the reinforcing steels were not corroded. The rehabilitation using the desalination and realkalization method increased the pH value to 12.6-13.2 and decreased water soluble chloride content to 0.47-0.56 kg/m3 around the reinforced bars in concrete of existing structures. During the 5-year-follow-up survey, re-diffusion of chloride ion into the concrete around the reinforced bars had been hardly recognized, and also the presence of clear shadow spot surrounding the reinforcing steel had not been recognized.
