Abstract
In recent years, inorganic-matrix reinforcement systems, such as fiber-reinforced cementitious matrix (FRCM), composite-reinforced mortars (CRM), and steel-reinforced grout (SRG), have been increasingly used to retrofit and strengthen existing masonry and concrete structures. Despite their good short-term properties, limited information is available on their long-term behavior. In this paper, the long-term bond behavior of some FRCM, CRM, and SRG systems bonded to masonry substrates is investigated. Namely, the results of single-lap direct shear tests of FRCM-, CRM-, and SRG-masonry joints subjected to wet-dry cycles are provided and discussed. First, FRCM composites comprising carbon, polyparaphenylene benzobisoxazole (PBO), and alkali-resistant (AR) glass textiles embedded within cement-based matrices, are considered. Then, CRM and SRG systems made of an AR glass composite grid embedded with natural hydraulic lime (NHL) and of unidirectional steel cords embedded within the same lime matrix, respectively, are studied. For each type of composite, six specimens are exposed to 50 wet–dry cycles prior to testing. The results are compared with those of nominally equal unconditioned specimens previously tested by the authors. This comparison shows a shifting of the failure mode for some composites from debonding at the matrix–fiber interface to debonding at the matrix-substrate interface. Furthermore, the average peak stress of all systems decreases except for the carbon FRCM and the CRM, for which it remains unaltered or increases.
Highlights
Inorganic-matrix composites represent a relatively new solution for strengthening and retrofitting existing reinforced concrete (RC) and masonry structures. They are based on the same principles of fiber-reinforced polymer (FRP) composites, where high-strength fiber sheets are coupled with polymeric matrices
Depending on the fiber and matrix type employed, inorganic-matrix composites can be referred to as fiber-reinforced cementitious matrix (FRCM) or textile-reinforced mortar (TRM), where open-mesh textiles and cement- or lime-based mortars are employed [4,5], textile-reinforced concrete (TRC), where high strength finely grained concrete embeds open-mesh textiles [6,7], or steel-reinforced grout (SRG), which are comprised of unidirectional steel cords and inorganic matrices [8,9]
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]
Summary
Inorganic-matrix composites represent a relatively new solution for strengthening and retrofitting existing reinforced concrete (RC) and masonry structures. Donnini et al [22] investigated the effect of freeze–thaw cycles and saline and alkaline environments on the tensile capacity of FRCM coupons made of AR glass textile and cement-based mortar. Nobili [23] studied the effect of saline and alkaline solutions on the tensile capacity of an AR glass FRCM and observed reductions in the range of 10% to 15% after 1000 h of conditioning depending on the type of matrix. The long-term bond behavior of inorganic-matrix reinforcements is investigated by exposing FRCM-, SRG-, and CRM-masonry joints to 50 wet–dry cycles and testing them using a single-lap direct shear test set-up. The results obtained were compared with those of nominally equal unconditioned specimens previously tested by the authors [11,28]
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