Thermal Compatibility and Bond Strength of FRP Reinforcement in Prestressed Concrete Applications

Due to concerns with corrosion, the use of fiber-reinforced polymer (FRP) as a replacement to conventional steel reinforcement has greatly increased over the last decade. However, when considering thermal gradients, many researchers have identified differential swelling between FRP reinforcement and concrete. This can lead to the development of splitting tensile stresses within the concrete cover surrounding the reinforcing bar and deterioration of the bond between the materials. A total of ten beams were therefore tested in flexure to investigate bond strength deterioration arising from thermal cycles ranging between −40 and +40°C. Beams were cast at +20°C and prestressed with either glass FRP (GFRP) or carbon FRP (CFRP) tendons. Additionally, the level of damage expected in the concrete cover of the specimens was predicted on the basis of linear elastic and nonlinear finite element analyses of thermally induced stresses. Although damage was theoretically expected, experimental results showed excellent bond performance of GFRP and CFRP tendons in concrete based on material properties and concrete cover requirements adopted for the project.