Pull‐off capacity of FRP–concrete composite bonded with epoxy/geopolymer at elevated temperature

Abstract

AbstractExternally bonded strengthening technique to the concrete has been widely used with epoxy adhesive. However, the adhesive is considerably weak against high temperatures, which has been regarded as the critical point in the loss of integrity of the strengthened system. Alternatively, geopolymer materials have shown an excellent performance at high temperatures, thus, their potential to be used as adhesive material has been investigated in this work. In experimentation, the composite specimens were developed using both types of adhesives, epoxy and geopolymer, and their performance was evaluated at three temperature levels (20, 60, and 120°C) by conducting pull‐off strength tests and classifying their failure modes. It was observed that the strength of concrete and epoxy was reduced with temperature. In contrast, the strength of geopolymer‐based adhesives strength was increased due to the reactivity of the precursor at high temperatures. Also, bond strength was reduced for both composite specimens at elevated temperatures. The highest bond strength was observed for the epoxy‐based adhesive system at 20°C, and about 70% loss in bond strength was observed when exposed to 120°C. The failure mode was also shifted from concrete to adhesive interface failure, that is, failure between the adhesive and the fiber fabric layer. The geopolymer‐based adhesive system has lower strength than its counterpart at all temperature levels, and the failure mode was adhesive interface failure. To enhance the bonding capacity at high temperatures, efforts are being made by adding different minerals has been employed. From the experimental results, it was found that there were some improvements, however, it was still less than that of epoxy‐based system. Further optimization of the geopolymer adhesive using minerals is required and then high‐thermal resistance geopolymer adhesive can be established.