Study of the Bond Capacity of FRCM- and SRG-Masonry Joints

Abstract

Fiber-reinforced cementitious matrix (FRCM) and steel-reinforced grout (SRG) have been increasingly applied as externally bonded reinforcement to masonry members in the last few years. Unlike fiber-reinforced polymer (FRP), FRCM and SRG have good performance when exposed to (relatively) high temperature and good compatibility with inorganic substrates, and they can be applied to wet surfaces and at (reasonably) low temperatures. Although numerous studies investigated the mechanical properties and bond performance of various FRCM and SRG, new composites have been developed recently, and their performance still needs to be assessed. In this study, the bond behavior of three FRCM composites and one SRG composite applied to a masonry substrate is investigated. Sixteen single-lap direct shear tests (four tests for each composite) are performed. The FRCM studied comprised one layer of carbon, PBO (polyparaphenylene benzobisoxazole), or alkali-resistant (AR)-glass bidirectional textile embedded within two cement-based matrices. The SRG composite comprised one layer of a unidirectional stainless-steel cord textile embedded within a lime-based matrix. The results show a peculiar bond behavior and failure mode for each composite. Based on these results, the behavior of the carbon and PBO FRCM is modeled solving the bond differential equation with a trilinear cohesive material law (CML).

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

“…SRG-masonry joints considered in this study generally failed due to debonding at the matrix-cord interface and rupture of steel cords [ 28 ]. The representative σ- g response of these joints ( Figure 3 ) is characterized by a linear and a subsequent non-linear ascending branches.…”

“…In general, the applied load is not evenly distributed among the cords due to the random variation of matrix-cord interface properties, which leads to progressive rupture of one or more steel cords, while some others continue to slip within the matrix. The occurrence of complete debonding (i.e., debonding along the entire bonded length) for some steel cords is confirmed by the occurrence of nonzero values of the free end slip s F close to the attainment of σ* [ 28 ].…”

“…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 textile bundles were spaced at 17 mm on center both in longitudinal and transversal direction. The fiber cross-sectional area in the textile warp direction was measured using the calcination method according to [ 32 ] and resulted slightly different from that reported in [ 28 ]. The tensile strength and elastic modulus of the AR glass textile were obtained by tensile testing of specimens comprising three longitudinal yarns according to [ 33 ] ( Table 1 ).…”

“…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 ].…”