Strengthening of shear-critical RC beams: Alternatives to externally bonded CFRP sheets

Extensive research has been conducted on strengthening of shear-critical RC beams. This previous research has helped to better understand the behaviour of shear strengthening systems and has improved their performance. However, there is still a potential to further improve upon the performance of existing shear strengthening systems. A cement-based composite system is an innovative strengthening system that shares many of the benefits of fiber reinforced polymer (FRP) systems (such as light weight, ease of installation and non-corroding) while overcoming some of the draw backs of epoxy-based FRP systems (including poor compatibility with concrete substrate, lack of vapour permeability and fire resistance). The current paper presents the results of an experimental study conducted to investigate the effectiveness of cement-based composite systems in comparison to an epoxy-based system (carbon fiber reinforced polymer, CFRP) to strengthen shear-critical RC beams. Two types of cement-based systems were investigated in this study: carbon fiber reinforced polymer (CFRP) grid embedded in mortar and carbon fabric reinforced cementitious mortar (CFRCM). The results showed that the cement-based systems (CFRP grid in mortar and CFRCM) perform better compared to the epoxy-based system (CFRP sheet) in terms of increase in shear capacity relative to ultimate strength of the strengthening systems. In addition, the CFRP grid embedded in mortar is the most efficient shear strengthening system due to its excellent bond to concrete.