Accelerated corrosion and repair of reinforced concrete columns using carbon fibre reinforced polymer sheets C. Lee, J.F. Bonacci, M.D.A. Thomas, M. Maalej, S. Khajehpour, N. Hearn, S. Pantazopoulou, and S. Sheikh Abstract: An experimental study on the simulation of corrosion in large-scale reinforced concrete columns and their repair using carbon fibre reinforced polymer (CFRP) sheets is presented. Seven columns were subjected to an acceler- ated corrosion regime, wrapped using CFRP sheets, then tested to structural failure and (or) subjected to further post- repair accelerated corrosion, monitoring, and testing. Accelerated corrosion was achieved by adding sodium chloride to the mixing water, applying a current to the reinforcement cage, and subjecting the specimens to cyclic wetting and dry- ing. Results showed that the CFRP repair greatly improved the strength of the repaired member and retarded the rate of post-repair corrosion. Moreover, subjecting the repaired column to extensive, post-repair corrosion resulted in no loss of strength or stiffness and only a slight reduction in the ductility of the repaired member. Key words: accelerated corrosion, carbon fibre reinforced polymer, composites, corrosion damage, corrosion rate, exter- nal confinement, reinforced concrete columns. Résumé : Une étude expérimentale de la simulation de la corrosion de colonnes en béton armé à grande échelle et de leur réparation par l’utilisation de feuilles de polymère renforcé de fibres de carbone (PRFC) est présentée. Sept colon- nes ont été soumises à un régime accéléré de corrosion, enrobées de feuilles de PRFC, puis ont été testées jusqu’à la défaillance structurale et/ou soumises à une corrosion accélérée additionnelle après réparation, une surveillance et des tests. La corrosion accélérée a été atteinte par l’addition de chlorure de sodium dans l’eau de mélange, l’application d’un courant à la cage de renforcement, et la soumission des spécimens à un cycle d’humidification et de séchage. Les résultats ont montré que les réparations avec le PRFC ont grandement amélioré la résistance du membre réparé et ont retardé le taux de corrosion après réparation. De plus, de soumettre une colonnes réparée à une corrosion intensive après réparation n’a causé aucune perte de résistance ou de rigidité, et n’a résulté qu’en une faible réduction de la duc- tilité du membre réparé. Mots clés : corrosion accélérée, polymère renforcé de fibres de carbone, composites, dommages par corrosion, taux de corrosion, coffrage externe, colonnes en béton armé. [Traduit par la Rédaction] Lee et al. 948 Introduction Reinforced concrete infrastructure represents a multi- billion dollar investment in North America, and premature deterioration due to corrosion has become an increasingly significant problem. Transportation structures such as rein- forced concrete bridge columns are especially vulnerable to corrosion attack because of their extensive exposure to de- icing salts. Briefly, steel in concrete is protected from corro- sion by the natural formation of a passive layer in the highly alkaline (pH > 13) environment that normally prevails in concrete. Chloride ions present in de-icing salts can cause the breakdown of this passive layer and initiate corrosion, provided that the chlorides, oxygen, and moisture are pres- ent in sufficient quantities at the level of the reinforcing steel. The effects of corrosion are three-fold: (i) it results in the dissolution of steel, causing loss of bar cross section and ductility; (ii) it generates expansive corrosion products, Can. J. Civ. Eng. 27: 941–948 (2000) © 2000 NRC Canada 941 Received August 4, 1999. Revised manuscript accepted March 1, 2000. C. Lee, 1 J.F. Bonacci, 2 M.D.A. Thomas, M. Maalej, 3 S. Khajehpour, 4 N. Hearn, 5 S. Pantazopoulou, 6 and S. Sheikh. Department of Civil Engineering, University of Toronto, Toronto, ON M5S 1A4, Canada. Written discussion of this article is welcomed and will be received by the Editor until February 28, 2001. 1 Current address: Halsall Associates Ltd., 2300 Yonge Street, P.O. Box 2384, Toronto, ON M4P 1E4. 2 Author to whom all correspondence should be addressed (e-mail: bonacci@civ.utoronto.ca). 3 Current address: Department of Civil Engineering, National University of Singapore, Singapore 119260. 4 Current address: Berger Lehman Associates, 411 Theodore Fremd Avenue, Rye, NY 10580, U.S.A. 5 Current address: Department of Civil and Environmental Engineering, University of Windsor, Windsor, ON N9B 3P4 6 Current address: Department of Civil Engineering, Demokritus University of Thrace, Xanthi, Greece 67100. Can. J. Civ. Eng. Downloaded from www.nrcresearchpress.com by University of Toronto on 12/30/14 For personal use only.