An Experimental Investigation into the Residual Bond of NSM Composite Strips for Concrete at Elevated Temperatures

This paper presents an initial experimental result concerning the behavior of near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) strips embedded in a concrete substrate at elevated temperatures. Thermal stresses varying from 25°C [77°F] to 200°C [392°F] are applied for three hours. The experimental program is comprised of 48 CFRP-concrete specimens bonded with an ordinary or high-temperature epoxy adhesive and their comparative performance is of interest in the present investigation. Emphasis is placed on the residual capacity of the conditioned NSM CFRP-concrete interface and corresponding failure mode. Test results show that the interfacial strength of the specimens bonded with the ordinary epoxy is maintained until 75°C [167°F] is reached, while the strength noticeably decreases with an increasing temperature above this limit. The specimens with the high temperature epoxy preserve interfacial capacity up to 200°C [392°F] despite a trend of strength-decrease being observed. The failure of the test specimens is brittle irrespective of adhesive type. Interfacial damage is localized along the bond-line with the presence of hairline cracks that further develop when interfacial failure is imminent.