Experimental characterization of the bond between externally bonded reinforcement (EBR) CFRP strips and concrete at elevated temperatures

Fire behaviour of FRP-strengthened reinforced concrete structural elements: A state-of-the-art review

“…Unsurprisingly, the available literature also confirms the superior bond performance at elevated temperature with either anchorage systems or adhesives with higher T g . Finally, these studies [31,35] have also confirmed the superior bond performance at elevated temperature of NSM as compared with EBR systems.…”

“…The first issue should be pursued in future studies as its influence on bond strength has yet to be confirmed and quantified. The second issue has been confirmed in various studies [31,35], however in which bond strength decreased within this temperature range. It is noteworthy that a common feature to all studies in which the bond strength increased at elevated temperatures below T g is that the specimens in these studies were all conditioned at elevated temperature for long durations (12 h or more) prior to structural testing.…”

“…6 show that generally, at temperatures moderately above T g , the bond strength may remain considerable. Firmo et al [31,35] have attributed such bond strength reserves to frictional forces at the bonded interface, particularly for NSM systems. Unsurprisingly, the available literature also confirms the superior bond performance at elevated temperature with either anchorage systems or adhesives with higher T g .…”

“…Regardless of the adhesive used, as in the companion study on EBR CFRP-concrete interfaces [31], elevated temperature caused a consistent reduction of bond strength, more linear strain distributions along the bonded length, an increase of effective bond length, bondeslip relationships with lower stiffness and maximum shear stress, and a change in the failure mode (from cohesive within the concrete block to adhesive at the CFRP-adhesive interface). The mixed grout presented considerably worse performance; this was attributed not only to its lower T g , but also to its inferior mechanical properties as well as its fine filler particles that were unable to promote friction at the bonded interface comparable to those developed with the epoxy adhesive (containing coarse filler).…”

“…Firmo et al [31] have recently performed double lap shear tests (Fig. 4) on concrete blocks with CFRP strips externally bonded with epoxy adhesive (T g of 47 C, determined by DMA) from 20 C up to 120 C. The effect of using a mechanical anchorage on the extremities of the CFRP strips was also investigated.…”