# Durability of Fabric-Reinforced Cementitious Matrix (FRCM) Composites: A Review
## 1 Introduction  
The use of fiber-reinforced polymer (FRP) composites to strengthen and retrofit existing masonry and reinforced concrete (RC) structures was proven to be an effective solution due to the FRP good mechanical properties, resistance to corrosion, and ease of application [1; 2; 3; 4]. However, some concerns raised regarding the poor sustainability and compatibility with the substrate of organic resins used in FRPs [5; 6; 7; 8]. In addition, organic resins produce toxic fumes when exposed to fire and lose their mechanical properties at temperature close to their glass transition temperature, which for resins commonly adopted in FRPs ranges between 45 \({}^{\circ}\)C and 82 \({}^{\circ}\)C [9; 10; 11].  
Fabric-reinforced cementitious matrix (FRCM) composites, which are also referred to as textile reinforced mortar (TRM) composites, were proposed as an alternative to FRP composites to overcome the drawbacks associated with the organic binders. FRCM are comprised of high strength fiber open-mesh textiles embedded within inorganic matrices. The textile can be made with different types of fiber, such as carbon, alkali-resistant (AR) glass, polyparaphenylene benzobisoxazole (PBO), or basalt. When steel fibers organized in steel cords are adopted, the inorganic-matrix composite is referred to as steel reinforced grout (SRG) [12]. The textile layout (dimension and shape of single yams, yarn spacing, and direction) can be varied to modify the textile-matrix stress-transfer mechanism and customize the composite behavior [10; 13]. In addition, textile yarns can be coated with organic resin to improve their bond with the matrix, FRCM ease of handling and installing, and to protect the fiber filaments. Various types of inorganic matrix can be found in the literature, such as cement-based and lime-based mortars and geopolymers, sometimes modified with fly ash, polymers, silica fume, and short fibers toincrease the adhesion to the textile and substrate [7; 14; 15; 16; 17; 18]. FRCM composites are generally employed as externally bonded reinforcement (EBR) for masonry [19] and RC members [20]. Inorganic-matrix composites comprising high-strength fiber textiles embedded within high-performance cement-based matrices were also used to construct high-strength panels often employed for new structural elements. These types of composite, referred to as textile reinforced concrete (TRC), have peculiar properties that make them generally different from FRCM composites [21; 22].  
Although an increasing number of experimental and analytical studies are available regarding the mechanical behavior of FRCM and TRC composites, limited work has been done to investigate their durability. Since they are externally bonded, FRCM can be exposed to various environmental conditionings, such as wet-dry (WD) and freeze-thaw (FT) cycles, high-alkalinity environments, and salt attack, which may affect their performance. The same holds for TRC composites when high-strength panels are used for outdoor applications. In this study, the available literature is reviewed to gain an insight on the state of research regarding mainly the long-term behavior of FRCM composites. In particular, (i) testing methods adopted to study the FRCM long-term behavior; (ii) accelerated ageing and conditioning environments considered to simulate the outdoor environments; and (iii) possible degradation of FRCM components (matrix and textile), FRCM coupons, and FRCM-substrate interface are analyzed and discussed. Based on this discussion, aspects that need to be further investigated are pointed out. When available, results of TRC composites are also analyzed to discuss their long-term behavior with respect to that of FRCM composites.