Environmental durability of externally bonded FRP-repaired concrete : effect of chloride ion penetration and temperature variation

Abstract

Fibre reinforced polymers (FRP) are used in a wide variety of applications in the construction industry. This dissertation aims to examine the performance and assess the durability of externally bonded fibre reinforced polymer (FRP) concrete, using one-directional FRP laminate strips, when subjected to various environmental exposure conditions. This was achieved by a literature review of similar studies on FRP concrete bond performance, then enhanced through a series of tests conducted on various samples, cast in the laboratory. Various environmental exposure conditions deduced from the local context were simulated in a lab and outdoor 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 harsh environmental conditions through numerous parameters and failure criteria using; 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 20 and 50°C, with 0, 50, and 100% relative humidity levels. Further samples were exposed to one week wet-dry cycles, and immersed in water with a 3% chloride (NaCl) solution by weight. 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. The results were compiled, analysed and discussed in order to relate the findings to the different environmental exposure conditions. Interesting findings were made on the effects of chloride ion penetration and temperature variations with respect to specimens conditioned at the lab and outdoor environment. In general, higher temperatures were found to have a greater impact on the degradation of the FRP-concrete bond. 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.