Cathodic protection has been proven to be one of the most widely applicable and cost-effective solutions for tackling steel corrosion in reinforced concrete. In this study, the possible use of carbon fibre composites, which are primarily used to strengthen concrete members, has been investigated as impressed current cathodic protection anodes. Carbon fibre anodes have been assessed in both concrete and calcium hydroxide solution. Two bonding mediums incorporating epoxy and geopolymer have also been investigated. The results demonstrate that epoxy resin can be used for bonding carbon fibre fabric anodes to reinforced concrete structures while geopolymer is more effective for bonding carbon fibre reinforced polymer (CFRP) rod into preformed grooves in the concrete surface. The dissolution of carbon fibre anode appears to stablise after a period of time, dependent upon the size and shape of the anode and applied voltage and current. Based on the present results, a maximum current density of 128？mA/m2 of reinforcing steel area is recommended for the operation of CFRP fabric anode and 64？mA/m2 of reinforcing steel area for that of CFRP rod anode. 1. Introduction Cathodic protection (CP) is a proven method of controlling corrosion in reinforced concrete through the application of a small DC current [1–4]. This can be applied either galvanically (e.g., by the preferential corrosion of zinc) or by an inert anode, referred to as impressed current cathodic protection (ICCP) [5–9]. In atmospherically exposed reinforced concrete structures, the successful application of ICCP depends significantly upon the selection of appropriate anode systems [10, 11]. There are a number of anode systems currently available; these include: conductive carbon loaded paints, thermal sprayed zinc, coated titanium expanded mesh or mesh ribbon in a concrete overlay, coated titanium expanded mesh ribbon mortared into slots chased into the concrete, internal (discrete) anode, and conductive cementitious overlay containing nickel plated carbon fibre [11, 12]. The properties of the anode materials need to be considered and researched carefully to ensure they operate effectively during their required service life. Cathodic protection systems require a level of monitoring, generally by reference electrodes, to assess how well the system is controlling corrosion. For ICCP systems in reinforced concrete, the current can be adjusted to the appropriate value to protect the steel reinforcement [13]. The effectiveness of ICCP depends greatly on the correct operation of the anodes, their electrical
References
[1]
US Federal Highway Administration, Memorandum on FHWA Position on Cathodic protection Systems, 1982.
[2]
P. Pedeferri, “Cathodic protection and cathodic prevention,” Construction and Building Materials, vol. 10, no. 5, pp. 391–402, 1996.
[3]
P. Lambert, “Cathodic protection of reinforced concrete,” Anti-Corrosion Methods & Materials, vol. 42, no. 4, pp. 4–5, 1995.
[4]
C. H. Haldemann and A. Schreyer, “Ten years of Cathodic protection in Concrete in Switzerland,” Corrosion of Reinforcement in Concrete: Monitoring, Prevention and Rehabilitation papers from Eurocorr ’97, European Federation of Corrosion Publication No.25. London, UK, Institute of Materials, 1998.
[5]
G. Mays, “Durability of Concrete Structures: Investigation, Repair, Protection,” Pub: E& FN Spon, 1992.
[6]
R. L. Kean and K. G. Davies, Cathodic Protection, DTI Publication, 1981.
[7]
L. Bertolini, F. Bolzoni, P. Pedeferri, L. Lazzari, and T. Pastore, “Cathodic protection and cathodic prevention in concrete: principles and applications,” Journal of Applied Electrochemistry, vol. 28, no. 12, pp. 1321–1331, 1998.
[8]
S. Szabó and I. Bakos, “Cathodic protection with sacrificial anodes,” Corrosion Reviews, vol. 24, no. 3-4, pp. 231–280, 2006.
[9]
S. Szabó and I. Bakos, “Impressed current cathodic protection,” Corrosion Reviews, vol. 24, no. 1-2, pp. 39–62, 2006.
[10]
J. P. Broomfield and S. El-Belbol, “Impressed Current Anodes for the Cathodic Protection of Atmospherically Exposed Reinforced Concrete,” CPA, Technical Note no.11, 2011.
[11]
X. Shi, J. D. Cross, L. Ewan, Y. Liu, and K. Fortune, “Replacing Thermal Sprayed Zinc Anodes on Cathodically Protected Steel Reinforced Concrete Bridges,” Final Report, SPR 682, 2011.
[12]
The Concrete Society, “Cathodic protection of steel in concrete,” Tech. Rep. 73, 2001.
[13]
B. S. Covino Jr., S. D. Cramer, S. J. Bullard, et al., “Performance of Zinc Anode for Cathodic Protection of Reinforced Concrete Bridges,” Final Report, SPR 354, 2002.
[14]
J. F. Bonacci and M. Maalej, “Externally bonded fiber-reinforced polymer for rehabilitation of corrosion damaged concrete beams,” ACI Structural Journal, vol. 97, no. 5, pp. 703–711, 2000.
[15]
The Concrete Society, “Design guidance for strengthening concrete structures using fibre composite materials, 3rd ed.,” Tech. Rep. 55, 2012.
[16]
M. Z. Jumaat, M. H. Kabir, and Obaydullah, “A review of the repair of reinforced concrete beams,” Journal of Applied Science Research, vol. 2, no. 6, pp. 317–326, 2006.
[17]
S. Gadve, A. Mukherjee, and S. N. Malhotra, “Corrosion of steel reinforcements embedded in FRP wrapped concrete,” Construction and Building Materials, vol. 23, no. 1, pp. 153–161, 2009.
[18]
E. W. Berver, D. W. Fowler, and J. J. King, “Corrosion in FRP-wrapped concrete members,” in Structural Faults and Repair, 2001.
[19]
L. K. Spainhour, I. A. Wootton, and N. Yazdani, “Effect of composite fibre wraps on corrosion of reinforced concrete columns in a simulated splash zone,” in Proceedings of the 3rd International Conference on Composites in the Infrastructure, San Francisco, Calif, USA, June 2002.
[20]
A. S. Debaiky, M. F. Green, and B. B. Hope, “Corrosion evaluation in CFRP wrapped RC,” in Proceedings of the 9th International Conference & Exihibition on Structural Fualts and Repair, Kensington, UK, 2001.
[21]
C. Lee, J. F. Bonacci, M. D. A. Thomas et al., “Accelerated corrosion and repair of reinforced concrete columns using carbon fibre reinforced polymer sheets,” Canadian Journal of Civil Engineering, vol. 27, no. 5, pp. 941–948, 2000.
[22]
C. V. Nguyen, P. S. Mangat, P. Lambert, F. J. O’Flaherty, and G. Jones, “Dual function carbon fibre strengthening and cathodic protection anode for reinforced concrete structures,” in Concrete Repair, Rehabilitation and Retrofitting III, Alexander, Ed., pp. 1179–1185, Taylor & Francis Group, London, UK, 2012.
