Durability of FRP-strengthened RC beams subjected to 110 months accelerated laboratory and field exposure

This paper presents an experimental investigation of the long-term performance of fiber reinforced polymer (FRP) composites strengthened reinforced concrete (RC) beams. The beam specimens had identical dimensions. Different FRP composites and adhesives were used, including carbon FRP (CFRP) plate bonded with Sika 30; CFRP plate bonded with Araldite 106; CFRP sheet bonded with SW-3C; and glass FRP (GFRP) bonded with Sika 330. Their performance was tested after 8, 18, 31, and 110 months of exposure to the wet-dry cyclic environment, and 48 and 110 months of exposure to the outdoor environment. Test results show that the FRP-strengthened RC beams subjected to the wet-dry cyclic environment exhibited more significant degradation compared to those subjected to the outdoor environment. In the wet-dry cyclic environment, CFRP plate/Sika 30 strengthened beams and CFRP sheet/SW-3C strengthened beams exhibited better durability performance with only 6 % and 4 % reductions in the flexural capacity after 110 months, respectively. In contrast, CFRP plate/Araldite 106 strengthened beams and GFRP sheet/Sika 330 strengthened beams exhibited larger reductions of 30 % and 31 %, respectively. Furthermore, the FRP debonding strain was reduced over time. A reduction factor is proposed for the design of FRP debonding strain based on test results to ensure long-term safety. © 2024 Elsevier Ltd.