Thermal Effects on Bond between FRP Rebars and Concrete

Bond between FRP bars and concrete depends on several parameters comprising environmental agents as the service temperature. As is known, FRP bars present high values of the transverse coefficient of the thermal expansion (CTE) with respect to concrete; as a consequence, when temperature increases, tensile stresses take place within the concrete that may produce splitting cracks affecting the bond performance. The present paper is devoted to the analysis of the bond between FRP bars and concrete under thermal loads taking into account already available data on bond–slip relationships and thermal behavior. An experimental investigation was carried out on concrete specimens reinforced with a FRP bar and subjected to thermal cycles with a maximum temperature value of 70 °C. After the thermal treatment, pull-out tests were performed at room temperature or higher. Untreated specimens were also tested for comparison. Results are reported and discussed in order to investigate the degradation of the concrete-reinforcement interface under thermal treatment and, as a consequence, the effects on bond–slip laws. Experimental results showed a significant degradation induced by exposure to relatively high temperatures.