Bond deterioration between near-surface mounted carbon FRP strips and concrete under moisture conditions

Near-Surface Mounting (NSM) Fibre-Reinforced Polymers (FRP) in concrete structures for strengthening is known to have many desirable benefits over external bonding. However, little is known about the durability of the critical bond between the embedded FRP and the concrete when installed using this technique. In this paper, recent experiment work into the durability testing of NSM joints, and their performance at member level are reviewed. Then, a shear bond test is devised to determine the effects of two types of moisture conditions, wet-dry cycling and continuous immersion in water. A total of 42 samples are prepared, consisting of two different grades of concrete substrate and three exposure periods of 14 days, 140 days and 238 days. Results suggest that the role of concrete strength development is of particular importance and that it is possible for the FRP to remain fully utilised by the joint despite prolonged exposure to moisture.