Thermal sensitivity of CFRP/Steel bond exposed to prolonged water ingress

Carbon Fiber Reinforced Polymer (CFRP) strengthened steel outdoor and submerged structures could be often exposed to water at a range of temperatures. According to the authors' knowledge, no study has identified the effects of water temperature on bond performance, even though a range of temperatures is experienced by the strengthened structures in different parts of the world. In addition, almost all studies focused on corroded steel strengthened with CFRP have been done on steel exposed to induced accelerated corrosion under laboratory conditions, which is not a correct representation of naturally corroded steel. The micro-level degradation occurs near the rusted surface due to hydrogen release from the corrosion process and may cause heavy degradation of the composite with prolonged exposure to an aggressive environment, which might not be observed from the samples with induced accelerated corrosion. Hence, it is important to evaluate the bond performance of the strengthened steel elements exposed to natural corrosion and subjected to prolonged exposure to water immersion while quantifying the effects of surface texture and temperature. A total of forty-eight steel specimens extracted from a naturally corroded steel bridge were selected. Two scenarios of surface roughness were induced by two surface preparation methods and the combined effects of temperature and moisture were key parameters. The prepared CFRP/Steel specimens were then conditioned in water at three different temperature levels for a pre-determined period of up to 1 year. The hot and cold weather exposed samples indicated a maximum strength reduction of 30 % and 18 %, respectively, while indicating the degradation in the bond line with high sensitivity to the surface roughness of the substrate.