Dual function carbon fibre reinforced anode system for concrete structures.

The corrosion of steel in concrete is one of the main factors causing the deterioration and damage of reinforced concrete structures where chloride diffusion or carbonation is likely, leading to the reduction of load capacity and service life of these structures. There are a number of techniques that have been developed to assist with this problem. Of these, cathodic protection has been demonstrated to be one of the most effective methods for the prevention and protection of steel from corrosion. More recently, carbon fibre composites have increasingly used to impart additional strength to existing reinforced concrete structures, including those suffering from corroded reinforcement. However, there has been a lack of research into the combined use of carbon fibre composites for both strengthening and the provision of cathodic protection (CP). This research investigates the requirements and limitations of operating carbon fibre based systems as both methods of strengthening reinforced concrete structures while simultaneously controlling the corrosion of the reinforcement through the application of CP by utilising the carbon fibre (CF) as an impressed current cathodic protection (ICCP) anode.The effect of anodic current density on the simulation of corrosion of steel in concrete has been investigated to allow specimens to be pre-corroded to a defined level prior to receiving the new anode and strengthening systems. The properties and electrical conductive of CF fabric and rods was tested for different candidate systems. Two bonding mediums, epoxy adhesive and a geopolymer have been used to bond CF fabric and rods to concrete. The dual function of the CF anode systems was tested on reinforced concrete beams with dimensions of 100mm by 150mm by 900mm and no shear reinforcement. The reinforcing steel was subjected to corrosion by the anodic impressed current method. CF fabric and rod anodes were used both for strengthening the corroded reinforced concrete beams and to provide ICCP. The potentials of the steel and potential decay resulting from the application of CP were monitored and analysed. Finally, the beams were flexurally tested to determine their deflection-load relationships. In order to improve the bond strength at the CF anode and concrete, U-shaped wrapping and a combination of geopolymer and epoxy as bonding medium was further researched. A series of tests has also been conducted to assess the effects of ICCP current on the bond strength at the steel to concrete interface. The results obtained show that anodic impressed current is a reliable method for accelerating the corrosion of steel in concrete. In addition, CF fabric and rod can be used as ICCP anodes while continuing to strengthen corroded reinforced concrete structures. The bonding at the CF fabric anode to concrete interface is improved by using U-shaped wrapping and the combination of epoxy and geopolymer is effective for improving bonding of the CF anodes. The applied ICCP current has been shown to result in a small reduction in the bond at steel to concrete interface, with higher applied currents resulting in a greater reduction in bond. This effect should be taken into account when designing any ICCP system.