162 / 2022-04-30 08:17:36

Experimental Study on the Repair Effect of Electrochemical Chloride Extraction for Corroded Reinforced Concrete

Electrochemical chloride extraction, Steel corrosion, Chloride extraction rate, Bond performance between concrete and steel

Electrochemical chloride extraction (ECE) is an effective rehabilitation method for reinforced concrete (RC) structures against steel-corrosion due to chloride attack. The application cases of ECE in Japan have been increased gradually according to the publication of guideline for electrochemical corrosion control method (Concrete Library 157; JSCE 2020, in Japanese).

However, there are few researches on the influence of the deterioration level of reinforced concrete on the repair effect of ECE. The repair effect might change due to the steel corrosion in concrete and cracks caused by the corrosion, since it changes the distribution of electrical current inside the concrete. To enhance the reliability of ECE, this study was conducted as an experimental investigation using RC specimens with different corrosion level for clarifying the influence of corrosion degree on chloride extraction efficiency and the property changes of cement paste and corrosion product.



In the experiment, ECE was carried out under the constant current condition (1344 A・h/m2) on specimens subjected to corrosion by the electrochemical corrosion acceleration. The steel corrosion degree in the specimen is shown in Table 1. Regarding the graph legends of Fig.3, Fig.4 and Fig.5, each number after the underscore indicates the current density and current application period of ECE.



The chloride extraction rate of specimen with slight corrosion or internal cracking caused by corrosion were comparable or higher than the rate of specimen with sound steel (Fig. 3). For specimens with corrosion cracks of about 0.2 mm with on the concrete surface, both pre-repaired and non-repaired specimens with crack injection material before applying ECE were examined. The chloride extraction rate in the area where the cracks were sealed by the crack injection material was similar to that of non-cracked specimen (Fig. 4). Within the scope of this study, pre-corrosion in reinforced concrete does not seem to have a negative effect on chloride extraction rate if the corrosion is not so progressed that cracks reach the surface of concrete. Even if surface cracks are observed, a certain level of chloride extraction effect can be expected if the cracks are filled by an appropriate pretreatment. Fig. 5 shows the maximum bond stress ratio from the pull-out test using round steel, indicating a decrease in bond stress due to ECE. It is also found that the effect of corrosion is not significant as long as cracks do not appear on the concrete surface even after applying ECE. The appearance of the specimen indicates that the corrosion products may have been passivated after applying ECE (Fig. 6), and it indicates that ECE may improve the protection effect against steel corrosion in concrete even if slight corrosion has progressed before applying ECE.