Experimental support for new electro active repair method for reinforced concrete

摘要

This paper, describes experiments that form the basis of an invention that aims at improving the durability of conventional (mechanical) repairs to concrete structures suffering from chloride induced corrosion of reinforcing steel. The invention comprises application of a short term, low voltage, DC current before or after concrete is broken out and before repair material is applied. It is an additional step in conventional concrete repair. The application of current will last typically 24 h at a current density of typically 5 A/m(2) of steel surface area. In laboratory experiments corrosion pits are simulated by placing highly concentrated iron(II) chloride solution in contact with a mortar surface, after which current is applied. The results indicate that this treatment is able to remove 90% or more of the chloride from the simulated pit solutions. Furthermore, the pH has increased from about 3 to more than 12. The combined reduction of chloride content and increase of pH strongly reduces the chloride to hydroxyl ratio of the pore solution and thus the aggressive conditions at the reinforcing steel. After applying alkaline chloride free repair material, this will result in a longer life of the repair, thus reducing the life cycle costs of repaired structures. The process is named EAR, electro active repair.