## 2 Long-Term Durability of Non-Metallic Reinforcement  
The long-term durability is affected by environmental factors such as stress, temperature, moisture and alkalinity (e.g., [17; 20]). These factors are not only used to simulate the environmental conditions, but also for artificial aging, as it is not possible to carry out long-term tests over a service life of up to 100 years [17; 21; 22; 23; 24; 25]. To determine the residual strength at the end of the life time, an extrapolation of the trend line based on the test data is necessary [16; 17; 26]. Tensile stress has the greatest influence on the long-term durability of non-metallic reinforcement. Depending on the level of stress, the load leads to a stress fracture of the filaments (creep rupture) after a certain time [27]. Micro cracks in the polymeric matrix appear due to the resulting stress in the yarns, which subsequently enable a chemical attack of the filaments [21]. Furthermore, the matrix can transfer less stress to the neighboring filaments in the area of the micro cracks. Due to the manufacturing process, the yarns are not exactly aligned, which leads to an uneven load when subjected to stress. However, it is expected that due to the internal composite stresses, the impregnation material creeps. This has a positive effect on the alignment of the filaments. Over time, the micro cracks may grow, which provokes a filament rupture when the ultimate strain or rather the ultimate stress is reached. Consequently, the load has to be transferred to the non-cracked filaments, which can lead to further filament rupture and finally the failure of the textile reinforcement [26]. The ambient temperature reflects the energy level. With increasing temperature, the energy level rises and chemical reactions are accelerated [18]. [PERSON] et al. [28] carried out fiber strand-in-cement strength tests with Cem-FIL AR glass fibers at temperatures from 20 \({}^{\circ}\)C to 80 \({}^{\circ}\)C and concluded that a chemical reaction controls the speed over the range of this temperatures. The long-term durability is also influenced by moisture. Moisture is present in every building component. Outdoor structures such as facade panels and bridges show an increased moisture level due to exposure to rain and melting snow. Many chemical reactions take place in concrete under the influence of moisture [29]. It serves as a transport medium for alkalis and other substances from the concrete or the environment to the reinforcement. According to [PERSON] and [PERSON] [30], a minimum moisture level must be exceeded before the transportation of moisture and OH-ions on the filament surfaces leads to a loss of strength of unimpregnated AR-glass reinforcement. For uncracked concrete components, the speed of the damaging process depends on the porosity of the concrete and the diffusion coefficient of the impregnation material of the textile reinforcement. In cracked components, moisture can penetrate faster through the impregnation material to the filaments due to cracks in the concrete matrix and micro cracks in the polymer matrix caused by stress in the area of the cracks [29], as described above. Besides the environmental factors, the long-term durability also depends on the material parameters of the non-metallic reinforcement. The filament material (e.g., carbon, glass and basalt), the impregnation material (e.g., epoxy resin, styrene-butadiene and vinylester), the cross-sectional area and the shape of the yarns, the transversal yarn spacing as well as the production process affect the long-term durability. Carbon filaments seem to be resistant under the environmental conditions. Carbon filaments do not undergo corrosion in alkaline environments nor absorb moisture [31]. In addition to that, the influence of the temperature on the durability of the carbon filaments is low. The temperature resistance of carbon even increases with production temperature [32]. However, strength losses may occur due to the impregnation material. The impregnation material serves to protect the filaments.