Mechanical properties of FRP-strengthened concrete at elevated temperature

- Ultimate tensile strength of FRP and MER decreased with temperature increasement.
- FRP-concrete bonding strength showed a decline trend as temperature increased.
- Fracture energy loss of FRP-strengthened members is more sensitive to temperature.
- Properties of FRP-strengthened concrete can be impaired due to high temperature.

This paper aims to illuminate the effects of elevated temperature on mechanical properties of fiber reinforced plastic (FRP) strengthened concrete glued by modified epoxy resin (MER) adhesive. Tensile strength, flexural strength and interface bonding properties of FRP-MER-concrete (C30 and C50) were measured after exposure to 80, 160 and 240 °C for 1.5 h and 3 h, respectively. Microstructures of the interface were analyzed by scanning electron microscope (SEM). The ultimate tensile strength and strain of MER-FRP, and bonding strength of FRP-concrete interface gradually decrease as exposure temperature and time increase. The ultimate capacity of FRP-strengthened concrete gradually decreases. The loss rates of ultimate capacity and fracture energy of high-strength specimens are greater than those of low-strength specimens. The fracture energy loss of FRP-strengthened concrete is more sensitive to temperature than to exposure time. The stress-strain relationship of FRP follows a bilinear behavior for both types of concrete. Micro-cracks in MER-concrete interface and concrete matrix degrade the mechanical properties of FRP-strengthened concrete at elevated temperature.