Lessons Learned on the Tensile and Bond Behavior of Fabric Reinforced Cementitious Matrix (FRCM) Composites

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 behavior 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 behavior 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, is outlined.

Low- and High-Cycle Fatigue Behavior of FRCM Composites

“…The matrix elastic modulus E m1 computed in this way from Stage I resulted 64% higher than E m (see Table 1 ). High values of E m1 were previously reported in the literature for various FRCM composites and can be attributed to uncertainties in the elastic modulus E m declared by the manufacturer [ 28 , 29 ]. The stress–strain response slope in the cracked stage, also referred to as the cracked elastic modulus [ 26 ], E 3 , resulted on average 12% higher than that of bare textile strips ( Table 1 ).…”

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

“…The coefficient of variation (CoV) varied between 6.4% (AR-glass FRCM) and 13.7% (PBO FRCM). This value (scatter) can be considered acceptable given the sensitivity of FRCM and SRG composites to the manufacturing, curing, and handling [22]. In order to compare the composite capacity, the capacity (peak load) per unit width can be considered.…”

“…Textiles are generally organized in a bidirectional open mesh configuration. The textile configuration (size, directions, and shape of single yarn, spacing between yarns) can be modified to provide specific properties to the composite [21,22]. Furthermore, textile yarns can be coated with resin to protect them, facilitate their handling and installation, and improve the matrix-fiber bond behavior.…”

“…FRCM and SRG have progressively become attractive for strengthening and retrofitting both masonry and concrete structures for their competitive cost, resistance to (relatively) high temperatures, compatibility with the substrate, and applicability on wet surfaces and at (reasonably) low temperatures. The main difference between FRCM for concrete or masonry applications lies in the matrix employed, which should be ad hoc engineered to optimize the compatibility with the substrate [21,22]. Numerous researchers [6,7,20,21,24] have been investigating the performance of various FRCM and SRG in the last decade, and the findings allowed for developing acceptance criteria and design guidelines for this type of composite [9][10][11].…”

Mechanical Response and Analysis of Cracking Process in Hybrid TRM Composites with Flax Textile and Curauá Fibres

“…Composites with inorganic matrices, generally referred to as Textile-Reinforced Mortar (TRM) systems, are getting more and more common for strengthening masonry structures, with a remarkable increase in the last decade due to their efficiency in enhancing bearing capacity against both in-plane an out-of-plane actions [1,2]. Several studies have been developed with the aim to define qualification procedures for the assessment of TRM systems subjected to tensile forces [3] and their bond behaviour with masonry substrates [4]. Moreover, scientific committees have formulated characterisation procedures for the definition of the mechanical behaviour of TRMs [5,6].…”