Behavior of Fiber-Reinforced Polymer Sheet-to-Concrete Bond under Elevated Temperatures

Glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) sheets bonded to concrete were investigated to evaluate bond behavior, including effective bond lengths under two conditions: sustained temperature (ST) or sustained load with increasing temperature (SL). Tests were conducted using either double shear or flexural shear. Effective bond lengths of 70 and 100 mm (2.8 and 3.9 in.) were inferred for GFRP and CFRP sheets, respectively, from the double-shear tests. The effective bond lengths were then used for elevated temperature specimens, which showed significant reductions in the bond strength beyond the glass-transition temperature (55°C [131°F]). For 60°C (140°F) ST condition, up to 73% and 52% bond strength reductions were observed in double-shear and flexure specimens, respectively. The elevated temperatures also shifted the failure mode from thin concrete shearing to adhesive failure. Due to adhesive failure, the SL specimens with 30% and 50% sustained loads failed around temperatures of 125 and 110°C (257 and 230°F), respectively, regardless of the fiber type.