# Durability of Fabric-Reinforced Cementitious Matrix (FRCM) Composites: A Review
## 4 Durability of Composite
### Durability of the Fibers  
Textiles used in FRCM can be made of carbon, AR-glass, PBO, aramid fibers, and steel (in the case of SRG). This section is dedicated to the durability of textile. Details of the tests included in the figures below are provided in Table 1. Although carbon fiber showed good durability [50; 51], it has a high cost in comparison with other fibers such as AR-glass or basalt. Basalt fiber is often compared to E-glass and AR-glass due to the similarities in the chemical structure [51; 52]. Limited results on the durability of PBO fibers employed in the civil engineering field can be found in the literature. AR-glass fiber is commonly used in civil engineering applications due to its availability and low cost. For these reasons, more results are available regarding the durability of AR-glass fiber than of other types of fiber. In the figures presented in this section, the blue color indicates tests at room temperature, whereas the orange color indicates tests at temperature equal to 60 \({}^{\circ}\)C.  
Figure 4: Effect of the alkaline environment on the matrices (blue bin = cement-based matrix and orange bin = lime-based matrix). To the authors' best knowledge, specific results of the freeze-thaw cycles long-term behavior of fiber textiles employed in FRCM composites are not available in the literature. Similarly, no results were found regarding the effect of sulfate exposures. The retained tensile strength of AR-glass fiber textiles subjected to various combined immersion in deionized water and temperature (hygrothermal environments) observed by different research groups is shown in Figure 5. [PERSON] et al. [51] reported no difference in the tensile capacity after 10 days of conditioning at 20 \({}^{\circ}\)C. However, [PERSON] et al. [53] reported a 15% reduction after 21 days of ageing. When the ageing temperature was raised to 60 \({}^{\circ}\)C, both [PERSON] et al. [51] and [PERSON] et al. [53] noticed a clear reduction in the strength, even larger than 60%. Nonetheless, [PERSON] [33] did not see a significant change of the textile tensile capacity at the same temperature (i.e., 60 \({}^{\circ}\)C). This conflict in the obtained results may be attributed to the difference in the coating materials of the fibers used by each research group. The fiber used by [PERSON] et al. [51] and [PERSON] et al. [53] was coated by 20% of styrene-butadiene resin (SBR) and vinylester, respectively, whereas the fiber used by [PERSON] [33] was coated by polyvinyl alcohol (PVA). In addition to the effect of coating, the difference in the textile layout and number of fiber filaments in each yarn may also have influenced the results. Figure 6 presents the retained tensile capacity ratio of AR-glass fibers immersed in seawater (3.5 wt. % of NaCl) for 1000 h (-42 days). At the room temperature, (ranging between 20 \({}^{\circ}\)C and 23 \({}^{\circ}\)C), [PERSON] et al. [34] and [PERSON] et al. [53] reported a small degradation of the tensile capacity. However, the degradation increased up to 40% when the conditioning temperature was raised to 60 \({}^{\circ}\)C.  
Figure 5: Retained tensile capacity ratio of AR-glass exposed to hygrothermal environments (blue bin = room temperature and orange bin = temperature equal to 60 \({}^{\circ}\)C). Figure 6: Retained tensile capacity ratio of AR-glass immersed in seawater (blue bin = room temperature and orange bin = temperature equal to 60 \({}^{\circ}\)C). The effect of the alkaline solution on the tensile capacity of AR-glass textiles is presented in Figure 7. At room temperature, different levels of degradation were reported (minimum textile retained tensile capacity ratio lower than 40%) depending on the alkalinity of the solution, exposure period, and fiber coating materials [34; 51; 53]. Besides, the degradation level increased with increasing the alkalinity and the exposure period. When the conditioning temperature was raised to 60 \({}^{\circ}\)C, the degradation level was increased especially in the case of [PERSON] et al.