Environmental durability of externally bonded FRP-repaired concrete

Abstract

Fibre reinforced polymers (FRP) are used in a wide variety of applications in the construction industry. The durability performance of externally bonded fibre reinforced polymer (FRP) concrete was assessed through an experimental investigation of concrete reinforced with one-directional FRP laminate strips, subjected to various environmental exposure conditions. Crushed coralline-limestone aggregate, C30/37 concrete was considered as the base material. Various environmental exposure conditions related to a marine environment were simulated in a laboratory and external environment, mainly to study the effect of chloride ion penetration and temperature variation. The behaviour of the FRP-concrete system was examined after exposed to aggressive environmental conditions through numerous parameters and failure criteria including single-lap shear, pull-pull off and 3-point bending tests. An experimental programme was prepared to investigate the behaviour of the FRP systems subjected to seven different environmental exposure conditions. FRP-concrete samples were conditioned to environments of 20oC and 50oC, with 0%, 50%, and 100% relative humidity levels. Furthermore, the FRP-concrete samples were exposed to wet-dry cycles, and immersed in water with a 3% by weight Sodium chloride solution. The single-lap shear test, pull-off test and the three-point bending test were used as standard test methods, to assess the FRP-concrete bond performance in shear, tension and flexure respectively. The behaviour and the mode of failure of FRP-concrete assemblies when exposed to chloride ion penetration and temperature variations, in a conditioned laboratory and an external environment, could be assessed. In general, higher temperatures were found to have a greater impact on the degradation of the FRP-concrete bond. Wet-dry cycles affected significantly the performance of ultimate bond strength as was also reported in previous studies [1, 2]. Exposure to water and NaCl solution respectively improved the bond between the composite materials in the initial stages of conditioning, while longer exposure periods resulted in a reduction in bond strength, as also reported in literature [3, 4]. From all environmental exposure conditions, the hydrothermal effects of high temperatures and water immersions were found to be the most detrimental, in all three types of tests. The research presents the performance of FRP-crushed coralline-limestone based concrete for different experimental parameters failure criteria, when exposed to aggressive environmental conditions.