Effect of heat aging on pull-off strength of FRP epoxy bonded concrete: An experimental study and fire modelling

Abstract

In this study, the bonding strengths of three different types of externally bonded composite systems were investigated under different environmental aging conditions at high temperatures, and the finite element model for a roof fire and concrete slab fire from above evaluated if the beams were externally reinforced with fiber- reinforced polymers (FRP). An FRP system is a structural reinforcement made of a type of fiber reinforcement fixed to a concrete surface through an epoxy adhesive. The bonding strength between the FRP and concrete substrates was measured using a pull-off test machine, as described in the EN 1542 standard. This study aims to determine the deterioration and negative effects of miscellaneous high temperatures on externally bonded FRPs used for strengthening civil structures. Epoxy-bonded carbon fiber-reinforced polymers (CFRP), glass fiber- reinforced polymers (GFRP), and basalt fiber-reinforced polymers (BFRP) were exposed to various temperatures of 23 degrees C degrees C (control conditions), 70, 85, 100, 115, 130, and 150 degrees C. degrees C. Duratek (R) (R) AV21 epoxy-based lamination system was used as an adhesive between the concrete and the FRP sheet. Three bonding failure modes (adhesive, cohesive, and substrate) were investigated for each test. The results were compared for three different types of FRPs under various temperatures, which is also significant research on the heat aging of the degradation process. The test results were also evaluated using finite element (FE) software modelling for roof and slab fires exposed from above, where the beams under the slab were reinforced with FRP systems. The test pull-off test results and FE model thermal analysis results were evaluated to obtain the temperature rise in the critical section of the concrete beam/slab in existing retrofitted buildings. The FE model results showed a critical temperature rise on the beam-slab corner connection as a result of the fire above the concrete slab. The duration of the FRP systems effectively bonded to the concrete beams located under different slab thicknesses and pull-off results were evaluated at elevated temperatures.