Elevated temperature response of RC beams strengthened with NSM FRP bars bonded with cementitious grout

Abstract

This paper presents the results of 12 tests on small-scale reinforced concrete beams strengthened in flexure with a single NSM carbon FRP bar. The used FRP bar is a novel commercial bar with high values of glass transition Tg and decomposition Td temperature to improve the performance of the strengthening system at elevated temperature. The FRP is bonded using a cementitious grout rather than an epoxy adhesive. Flexural tests were performed at both ambient and elevated temperatures on both un-strengthened and strengthened beams. Tests at elevated temperature were performed using propane-fired radiant panels, rather than a fire testing furnace, in two heating configurations (localised heating near midspan only and global heating over the entire bonded length of the FRP systems).This paper also shows the results of Dynamic Mechanic Analysis (DMA), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) tests conducted on the CFRP. The results of thermal conductivity tests of CFRP and cementitious grout, and tests conducted to define the mechanical properties of concrete, steel bars, cementitious grout and CFRP bar are discussed herein.The flexural tests demonstrated the grout-bonded NSM CFRP strengthening system’s ability to maintain structural effectiveness at temperatures up to about 600 °C with adequate anchorage. However, similar tests with an epoxy adhesive are needed before the novel system can be confidently stated as being vastly superior to epoxy-adhered NSM systems.