Compressive strength of FRP-confined concrete at elevated temperatures

Many research studies have shown that fibre-reinforced polymers (FRPs) can be efficiently, economically, and safely used for strengthening and rehabilitation of reinforced concrete structures. However, relatively little is known about the behaviour of FRP materials at high temperature, and this is a primary factor that is limiting the widespread application of FRP materials in civil engineering structures. This paper presents the results of an experimental programme to investigate the effect of high temperature on the performance of concrete cylinders externally confined with fibre-reinforced polymer (FRP) sheets. For this purpose, 42 small-scale concrete cylinders measuring 100 × 200 mm were cast. Of these 42 specimens, 14 specimens were left unwrapped to be used as baseline or control specimens, 14 specimens were wrapped with one layer of CFRP sheets, and the remaining 14 specimens were wrapped with GFRP sheets. These specimens were exposed to room temperature and heating regimes of 100 and 200°C for a period of 1, 2, and 3 h. The specimens were tested in compression, and their performance was evaluated after they had been exposed to specific heating regimes. The test results demonstrate that, at a temperature around the glass transition temperature (Tg) of the resin, CFRP- and GFRP-wrapped specimens experienced a small loss of strength, resulting from melting of epoxy. This damage was more pronounced when the temperature reached 200°C. ©Smithers Rapra Technology, 2008