Exploratory Study on ECE Technique for Chloride Removal from Concrete Beams Retrofitted with FRP Strips

The application of Fiber-Reinforced Polymer (FRP) composites for retrofitting deteriorated concrete structures has been highly successful, but there are concerns with long-term performance and durability, particularly when chloride ions are still present for two possible reasons: (1) no chloride ion extraction is performed when a bridge is initially retrofitted; and (2) even if chloride ions are initially extracted, they will again accumulate from available sources such as continual application of de-icing salts. Leaving chlorides within concrete will exacerbate the onset of corrosion during the post-repair service life of the structure. Therefore, it is desirable to study whether the Electrochemical Chloride Extraction (ECE) technique, which has been proven to be an effective tool for removing chloride ions for regular concrete structures, can be effectively used for FRP repaired structures, which is the objective of this study. A total of 28 beams were tested. Testing variables included different ECE techniques, i.e., intermittent vs. continuous; different FRP repairing schemes; and applying ECE before and after FRP repair. Parameters monitored during the study included chloride content, pH value around the steel, and current resistance and density. The effectiveness of ECE was determined by changes in chloride levels and the pH value around the steel. At this stage of the study, only partial results for concrete beams without FRP are reported, while the overall scope of the research is described. Based on this study, the effects of different testing variables will be evaluated, a modified ECE technique will be proposed, and guidelines for how to implement the technique on FRP repaired structures will be provided.