Bond behavior of NSM FRP bars at elevated temperatures

The weak performance of FRP (Fiber Reinforced Polymer) strengthening systems at elevated temperatures due to fire exposure is a primary factor that prevents the widespread application of FRPs in buildings. The low fire resistance can be attributed to the relatively poor performance of both adhesive and FRP matrix polymers at temperatures beyond the glass transition temperature. When reaching the glass transition temperature, the properties of the adhesive decrease to a large extend and bond interaction between the concrete and the FRP reinforcement may be completely lost. In the case of NSM (Near Surface Mounted) the FRP reinforcement is not longer externally bonded, but in slits. This offers extra protection to the high temperature or fire exposure. To study the bond behavior at elevated temperature between the NSM FRP bars and the concrete a series of 18 double bond shear tests were performed at Ghent University. The present paper will discuss the experimental work and the main test results obtained