Abstract
Fabric Reinforced Cementitious Matrix (FRCM) composites represent an effective, compatible and cost-efficient solution for strengthening and retrofitting existing structures. A strong research effort was done to investigate the tensile and bond properties of these materials, as well as the overall behaviour of strengthened members. A Round Robin Test was organized by Rilem TC 250-CSM on 28 FRCM composites comprising basalt, carbon, glass, PBO, aramid and steel textiles, embedded in either cement, lime or geopolymer mortars, to collect an experimental dataset and define test protocols. This paper collects the outcomes of this study to highlight fundamental properties of FRCM and to investigate the variability of test results. Grid spacing, equivalent thickness of the textiles and mechanical properties of FRCM composites, such as stiffness, tensile and bond strength, are provided. Based on the comparison of experimental outcomes, the scatter of the mechanical properties is estimated, as a consequence of the quasi-brittle behaviour of the inorganic matrix and its sensitivity to manufacturing, curing and handling processes. Eventually, the influence of testing implementation, such as gripping method and measuring techniques, are outlined.
Highlights
Bonded (EB) reinforcements with inorganic-matrix composites are a effective solution for repairing and strengthening existing concrete and masonry structures
The 23 Fabric Reinforced Cementitious Matrix (FRCM) systems included in the analysis of this paper comprised 22 different textiles, 2 of which were made of aramid, FIGURE 2 | Direct tensile tests on FRCM composite specimen (A) and shear bond tests on masonry substrate (B)
Despite a significant variability from system to system, as a general trend, the lowest values were obtained for glass FRCM composites, whereas the highest ones for carbon and PBO ones and for Steel Reinforced Grout (SRG)
Summary
Bonded (EB) reinforcements with inorganic-matrix composites are a effective solution for repairing and strengthening existing concrete and masonry structures. Lime-based mortars ensure physical/chemical compatibility with masonry substrates, vapor permeability, and reversibility, complying with the principles of conservation of architectural heritage For all these reasons, FRCM systems are considered competitive, or even preferable in some cases, over Fiber Reinforced Polymers (FRP), which employ epoxy or polyester resins, even if organic binders may provide a higher substrate-to-composite bond capacity than mortars. The crucial issues of the reliability and repeatability of test results have not been deeply tackled yet, because of the lack of wide experimental and consistent datasets To this purpose, a Round Robin Test (RRT) was organized by the Rilem TC 250-CSM (Composites for the Sustainable Strengthening of Masonry) and Assocompositi (Italian Industry Association for Composite Materials). The same system was tested by at least two institutions ( results on aramid systems were available only from one institution), which allowed for comparing the results and analyzing the effect of the experimental setups and testing
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