Effect of hot temperature on pull-off strength of FRP bonded concrete

• Identify various interfacial failure modes of FRP bonded concrete.
• Review requirements for achieving bond bonds between FRP and concrete.
• Discuss bond testing issues.
• Determine bond strength deterioration under high temperature environments.

In recent years, thin fiber reinforced polymer (FRP) composite sheets have been successfully used in strengthening deficient concrete structures. Although the short term performance of these FRP sheets has been satisfactory, their long term durability performance remains yet to be confirmed. The bond strength between FRP and its concrete substrate is one of the critical design factors due to the composite action requirement. In this paper, the effects of hot temperature (100 and 180 °C) on the deterioration of bond strength and the changes in failure modes are presented and discussed. Three possible failure modes are considered in this study: cohesive in the concrete substrate, mixed, and adhesive at the interface. Therefore, the true bond strength between concrete and FRP can only be measured when the failure mode is adhesive. Under the control conditions at room temperature, the true adhesive strength exceeds 6 MPa, which is adequate for most engineering applications. A combination of high temperature and low humidity is the most detrimental to bond strength.