A bending test set-up for the investigation of the bond properties of FRCM strengthenings applied to masonry substrates

Existing masonry and reinforced concrete structures are characterized by a wide use of structural and non-structural masonry members such as structural walls, infill walls, arches, vaults etc. All these members are characterized by high vulnerability when subjected to seismic events, since unreinforced masonry has a negligible tensile strength. The use of fiber reinforced polymers (FRP) composites has become a common practice and it represents a light-weight, easy, fast, and non-invasive solution for rehabilitation of existing masonry structures. Fabric reinforced cementitious matrix (FRCM) are relatively newly-developed composite materials, representing a valid alternative to FRP in strengthening and retrofitting of existing reinforced concrete and masonry structures. Despite of the numerous advantages guaranteed by the inorganic matrix, the bond behavior between the fibers and the embedding matrix is still under investigation. Different set-ups have been proposed in the literature to study the bond behavior of FRCM composites. Among them, single- and double-lap direct-shear tests are the most commonly used. In this paper, the bond behavior of a polyparaphenylene benzobisoxazole (PBO) FRCM composite applied to masonry elements is studied using a bending and a single-lap direct-shear test set-up. The bond capacities obtained by the two set-ups are analyzed and discussed.