Geopolymer adhesive for sustainable NSM CFRP strengthening of RC structures

Abstract

Carbon fiber reinforced polymer (CFRP) composites are known to be a very effective materials for strengthening and rehabilitation of reinforced concrete (RC) structures. Near surface mounted (NSM) technique, has been used as an effective method for this purpose, over the past two decades. The conventional technique benefits from the superb properties of polymeric adhesives like epoxy resins, to ensure a successful transfer of stresses between the CFRP and concrete substrate. However, the vulnerability of polymeric matrices to high temperatures motivated researchers to focus on developing cement-based adhesives for NSM CFRP systems for special applications where fire safety is an issue. Recently, efforts led to promising outcomes for the future of these novel systems. This upgrade not only fulfills the fire safety measures but also is necessary from the environmental point of view, due to the pollution and health problems associated with the usage of epoxy resins as conventional adhesives for FRP systems. While improvements occurred in the bond performance of the NSM CFRP systems with cement-based adhesives, using innovative sand-coated CFRP strips, the alternative sustainable approaches could be also investigated. This paper is dedicated to assessing the adoption of a geopolymer adhesive, to serve as a matrix for NSM strengthening techniques, using special sand-coated CFRP strips. Bond tests have been performed in ambient and thermo-mechanical conditions, and results showed promising performance of adoption of geopolymer in this technique. Also, a brief analysis of the environmental impact of using geopolymer as an alternative sustainable matrix is discussed, compared with epoxy resin and cement-based adhesive as its competitors, for eco-friendly strengthening systems for RC structures.