Durability of the adhesive bond between continuous fibre sheet reinforcements and concrete in an outdoor environment

The authors set out to investigate the durability of the bond between carbon fibre (CF) sheet reinforcement and concrete. They conducted an outdoor exposure test in a moderate climate for 14 years and an immersion test for 6 months on CF sheet bonded to concrete, and then evaluated the adhesive bond properties using the pull-off and peel methods.The pull-off strength slightly decreased after 14 years of exposure, but residual values still indicate quite good adhesive properties. The failure modes for both the initial specimens and the specimens after 14 years of exposure consisted of concrete substrate failures in all cases. This result suggests that the slight decrease in pull-off strength does not necessarily indicate a change in the properties of the bond between CF sheet and concrete. On the other hand, results of the peel tests showed different types of failure modes and seemed more discriminant than those of the pull-off method.As regards specimens immersed in water, pull-off results were in few cases consistent with the peel characterizations, showing significant evolutions in the strength and failure mode. But for most specimens, the two methods provided divergent trends. In the end, this study suggested that the peel test could be relevant for evaluating the durability of the bond between CF sheet and concrete, while the representativeness of the pull-off test remains a matter of discussion.