## 3 Results and Discussion
### Evaluation of the Composites' Behavior Subjected to Physical Attacks
#### 3.2.2 Wetting-Drying in 3.5% NaCl Solution  
The generally observed behavior was similar to that for wetting-drying in water at both the strength and toughness levels. Evidently, the attack decisively affected the stability of composite C (Figure 8a), with a progressive drop in mechanical behavior close to 8 MPa after 50 cycles being observed. The composites with pozzolans that underwent SC displayed improved properties, which were favored by heat treatment (drying step) during cycles. Such behavior obtained a maximum value after 10 cycles, slightly decreased up to 50 cycles, and values remained close to 10 MPa. For the Acc samples, a slight decrease took place with the cycles, although a similar or higher strength than 10 MPa was recorded. With the pozzolan-containing composites, toughness (Figure 8b) progressively decreased with the number of cycles, whereas very significant embrittlement was observed for the control composite and, once again, after 10 cycles. These results imply that the presence of NaCl did not significantly affect the stability of the fibers in the cementing matrix.  
Significant fiber deterioration was observed for the control composite (C) after 50 cycles (Figure 9). Craters appeared on the surface of fiber filaments and hydration products were seen, especially calcium hydroxide crystals, which were embedded in the surface. When evaluating the chemical composition (Table 5) at the points of interest marked in the micrograph, the presence of hydrated calcium silicoaluminates was seen in spots 1 and 2  
Figure 8: Modulus of rupture (**a**) and toughness (**b**) for the GRC composites subjected to wetting–drying tests in 3.5% NaCl solution.  
(at this point, the sodium and chlorine percentages were significant), and portlandite was mostly observed in spot 3.  
The TGA information presented in Table 6 shows the changes in the cementing matrix evolution. We can see that the percentage of combined water of the hydrates for the systems with pozzolanic substitution is lower after SC, but increases after 50 cycles. This fact confirms the improved composite properties and progressive cementing hydrate production. After curing 28 days, only calcium hydroxide remains in the control composite, whose value lowers when applying cycles because part of the portlandite dissolves when reacting with the chlorides present in solution and [PERSON]'s salt originates [31] (identified on the TGA curve, with mass loss centering at 300-400 \({}^{\circ}\)C).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Composite**} & \multicolumn{2}{c}{**\% Combined Water from Hydrates**} & \multicolumn{2}{c}{**\%Ca(OH)2**} \\ \cline{2-5}  & **Standard Curing** & **After** & **Standard Curing** & **After** \\  & **28 Days at 20 \({}^{\circ}\)C** & **50 Cycles** & **28 Days at 20 \({}^{\circ}\)C** & **50 Cycles** \\ \hline C & 10.27 & 12.17 & 7.98 & 4.67 \\ \hline CFA60 & 7.39 & 12.26 & 0.00 & 0.00 \\ \hline CFA50+SSF10 & 9.50 & 12.03 & 0.00 & 0.00 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Thermogravimetry results on the composites subjected to wetting–drying tests with 3.5% NaCl solution.  
Figure 9: SEM micrographs of the fibers in the control GRC composite subjected to wetting–drying test with 3.5% NaCl.