Experimental procedures for the mechanical characterization of composite reinforced mortar (CRM) systems for retrofitting of masonry structures

Abstract

Fiber-reinforced composites can be arranged in the form of bi-dimensional grids and employed as internal reinforcement of mortar plasters to realize composite reinforced mortar (CRM) systems. Recently, CRM were applied as externally bonded reinforcement of existing masonry members showing promising improvements of load-carrying and deformation capacities. However, since CRM systems are still in their infancy, limited research is available regarding their mechanical properties and their bond behavior with respect to masonry substrates. In this paper, a series of experimental tests are performed on a CRM system comprising a glass fiber-reinforced composite grid and a lime-based matrix. Namely, tensile tests of bare grid yarns and of CRM coupons, shear tests of grid joints, and single-lap direct shear tests of CRM-masonry joints were performed. These tests are aimed at providing a comprehensive mechanical characterization of the CRM, which results can be used to design strengthening applications with this system. Namely, the tensile properties of bare grid yarns in warp and weft direction are obtained and compared with those of CRM coupons tested following the indications of the Italian and U.S. acceptance criteria for inorganic-matrix composites. Furthermore, the grid joints are subjected to shear tests to determine if the yarns orthogonal to the applied load direction provide a contribution to the system load-carrying capacity. Finally, CRM-masonry joints are subjected to single-lap direct shear tests to study the CRM bond behavior. This work provides an insight on the behavior of CRM that can be useful to formulate reliable design procedures for these systems.

Effect of Wet-Dry Cycles on the Bond Behavior of Fiber-Reinforced Inorganic-Matrix Systems Bonded to Masonry Substrates

“…Six specimens were prepared for each type of reinforcement and were all subjected to wet–dry cycles prior to testing. Nominally equal unconditioned specimens were presented and discussed in [ 11 , 28 ] and are considered here for comparison.…”

“…The grid was spaced at 40 mm in both directions and was embedded within the same NHL 5 mortar used in the SRG [ 36 , 38 ]. The mechanical properties of the grid and mortar were evaluated in [ 11 ].…”

“…The bonded length of the FRCM and SRG composites was 300 mm, as recommended by the Italian acceptance criteria for inorganic-matrix composites [ 33 ]. The bonded length of the CRM strips was 290 mm, which is the maximum bonded length possible for the masonry blocks employed (the strip end shall not coincide with the masonry block edge to avoid wedge failure) and the same considered in [ 11 ] to study the bond behavior of CRM-masonry joints. The width of the composite strip b 1 was selected to be a multiple of the warp yarn spacing and was equal to 50 mm for FRCM and SRG composites, whereas it was 120 mm for the CRM system.…”

“…Recently, systems made of composite grids embedded within inorganic matrices, which are referred to as composite-reinforced mortar (CRM), have been increasingly adopted as externally bonded reinforcement of masonry members [ 10 ]. CRM systems are particularly attractive because of their simplicity of installation and low price [ 11 ].…”

“…This condition may be representative of the intrados of bridges subjected to cyclic floods [ 27 ]. The results obtained were compared with those of nominally equal unconditioned specimens previously tested by the authors [ 11 , 28 ].…”