## 3 Test Results and Discussions
### Effect of the High Temperature and Humidity Environment  
The second test series that included the HTHE, HTHE_E, and HTHE_ES coupons was prepared to investigate the effect of a high temperature and humidity environment on the tensile behavior of TRM coupons. The HTHE coupons mean the TRM coupons without surface treatment subjected to the high temperature and humidity environment. Similarly, the HTHE_E and HTHE_ES coupons refer to the TRM coupons with epoxy impregnation, and the TRM coupons with sand coating after epoxy impregnation, respectively.  
Figure 15 shows the stress-strain relationship of the TRM coupons with different surface treatment methods in the high temperature and humidity environment. In the uncracked stage, the TRM coupons in this series showed almost the same initial stiffness values (Figure 16a and Table 2). The crack pattern and failure mode in this series were the same as in the first series (Figure 9b). In addition, Figure 16 shows the average values of ultimate strain, cracking tensile strength, and ultimate tensile strength of TRM coupons. As presented in Figure 16a, the cracking tensile strengths were almost the same, but the ultimate tensile strengths of the HTHE_E and HTHE_ES coupons showed a slight decrease of 10.09%  
Figure 14: Tensile stress–strain relationship of TRM coupons under sound conditions: (**a**) coupons without surface treatment; (**b**) coupons impregnated by epoxy; (**c**) coupons coated with aluminum oxide powder after epoxy impregnation.  
and 12.53% compared to that of coupons HTHE, respectively. In contrast, the ultimate strain of the HTHE_E and HTHE_ES coupons showed increases of 25.50% and 12.53%, respectively, compared to that of coupons HTHE. The results show that the high temperature and humidity environment affected the bond strength and deformability at the fabric-mortar interface. During the tensile test, longitudinal cracking at the side of the test coupons HTHE and HTHE_E was also observed (Figure 9b).  
Figure 17 shows the tensile stress-strain relationship of TRM coupons subjected to the high temperature and humidity environment. Figure 17 shows that the HTHE coupons subjected to the high temperature and humidity environment revealed a significant reduction in stiffness, but a slight reduction in strength, and a slight increase in strain compared to that of the Com coupons. In addition, in the Com series, the positive effect of the surface treatment on the tensile behavior was significant, while that in the HTHE series was not significant.  
Figure 16: Effect of different surface treatments on the tensile behavior of TRM coupons in the high temperature and humidity environment: (**a**) cracking and ultimate strength; (**b**) initial stiffness; (**c**) ultimate strain.  
Figure 17: Tensile stress–strain relationship of TRM coupons subjected to the high temperature and humidity environment: (**a**) coupons without surface treatment; (**b**) coupons impregnated by epoxy; (**c**) coupons coated with aluminum oxide powder after epoxy impregnation.  
Figure 15: Tensile stress–strain relationship of TRM coupons with different surface treatments in the high temperature and humidity environment: (**a**) coupons without surface treatment; (**b**) coupons impregnated by epoxy; (**c**) coupons coated with aluminum oxide powder after epoxy impregnation.