Bond behavior between fiber reinforced composites and quasi-brittle material interfaces

The present dissertation presents an investigation of the bond behavior of newly developed fiber reinforced composite systems applied to quasi-brittle material interfaces. Direct shear tests were performed on steel reinforced polymer (SRP) and steel reinforced grout (SRG) composite strips applied to both concrete and masonry substrates. Different types of cementitious matrices and different densities of steel fiber sheets were employed. Tests were performed investigating several parameters, i.e. bonded width, bonded length, loading rate, and face to which the composite strip was applied. Failure modes and load responses were presented and discussed. It was observed that the fracture energy GF of SRP-concrete joints is independent of the composite density but varies as the composite is bonded to different faces of the concrete prism. The width effect was considered in the evaluation of the load-carrying capacity of SRP-concrete joints, while the loading rate influenced the peak load of both SRP and SRG specimens. The behavior of SRP-concrete joints was also investigated through a numerical analysis, using lattice discrete particle model (LDPM), obtaining an excellent match with the experimental results. Some concrete prisms were reinforced and tested using a geopolymer matrix that showed interesting results. Some masonry specimens were subjected to artificially weathering cycles to investigate the durability performances of SRG strips with respect to salt attack. Furthermore, monotonic compressive tests were performed on concrete columns confined with both SRP and SRG composites. Several parameters were investigated, i.e. the density of steel fiber sheets, the concrete corner condition, the overlapping length, the number of confinement layers, the scale effect, and the shape effect. Failure modes and load responses were presented and discussed. Finally, several applications of basalt-fiber reinforced cementitious matrix (B-FRCM) composites bonded to masonry substrates were showed, including full scale tests on existing masonry arches.