The long-term effectiveness of electrochemical chloride extraction as remediation for corroding steel in reinforced concrete

Steel reinforced concrete blocks were subjected to electrochemical chloride extraction after they were dosed with chlorides. Following treatment, the blocks were exposed to the elements at the BRE exposure site for a period of up to 6 years. A selection of blocks were cut into smaller steel-containing prisms after 4 ½ years of exposure and were exposed to controlled laboratory conditions for 6 months while determining the level of corrosion by linear polarisation. At termination, each steel bar was removed and examined visually. The level of corrosion of each bar was also assessed gravimetrically. The final chloride concentration profile of each prism to a depth beyond the steel bars was also determined. Results suggested that corrosion was reduced significantly following chloride extraction but that the primary controlling factor, both for the desalinated and control specimens, was the level of chloride present at the depth of the steel reinforcement. Coating the concrete after treatment resulted in an overall increase in corrosion level, possibly because the coatings were not coherent and allowed moisture to penetrate the concrete through cracks and defects which could not subsequently escape owing to the coating.