## 3 Results and Discussion
### Assessment of the Behavior of the GRC Composites Subjected to Chemical Attacks
#### 3.3.1 Exposing the GRC Composites to a NH4 Cl Solution  
Figure 11 shows the variation in mass that specimens underwent when exposed to the aggressive medium. The initial mass was reduced in all cases. Greater loss occurred for the control specimen, C, because of the decalcification of the matrix, specifically dissolution of portlandite, and decomposition of C-S-H [32]. After 216 exposure days, this loss was close to 14%. For the specimens with pozzolans and SC, much less mass loss took place compared to the control, given the mass loss values of between 5% and 7% after 216 days. The pozzolanic composites with Acc were those with the least loss (4-5%). This behavior was directly related to the increase in density and the lowering degree of water absorption. For these cementing matrices, portlandite content was measured (0% Ca(OH)2) by the TGA test), which means less leaching of the matrix by acid-base reactions. [PERSON] et al. [33] demonstrated the effect of pozzolans on the leaching reduction of calcium in cement-based materials.  
Figure 12 shows mechanical composite behavior before and 28 days after the NH4 Cl attack. When evaluating the modulus of rupture (Figure 12a), and after being immersed in the solution for 28 days, the strength of all the mortars decreased. One very important fact was that the GRC composites with Acc were clearly maintained over the control GRC. The hydrated products from the pozzolanic reaction were much more resistant to the ammonium chloride attack, and the reaction to portlandite was not possible. When assessing toughness (Figure 12b), the pozzolan-containing composites better responded to the aggressive agent than composite C. For 28 curing days, all the composites obtained high toughness values. After being exposed to the aggressive environment, the control composite's toughness decreased with values close to zero (brittle fracture). Although the toughness of the GRC with pozzolans decreased after being exposed to the aggressive agent, their behavior was notably superior than the control, C.  
Figure 11: Mass variation for the GRC composites immersed in a 1 molar (1 M) NH4 Cl solution.  
Table 7 shows that calcium hydroxide was present only in composite C after 28 curing days, a value that lowered when the attack was applied because portlandite dissolves when it reacts with the ammonium cation (NH4+) present in the aggressive solution. When analyzing the combined water of hydrates, 0.13% corresponded to Friedel's salt, produced by the reaction among calcium aluminate hydrate, calcium hydroxide, and the chloride anion [34]. In the systems with pozzolan, all the portlandite was consumed by the high proportion of pozzolan by modifying the aggressive environment for fibers and reducing acid attack leaching.  
\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** & **Immersed for 28** & **Standard Curing** & **Immersed for 28** \\  & **28 Days at 20 °C** & **Days in NH4 Cl** & **28 Days at 20 °C** & **Days in NH4 Cl** \\ \hline C & 10.27 & 13.76 * & 7.98 & 0.00 \\ GFA60 & 7.40 & 9.10 & 0.00 & 0.00 \\ GFA50+SSF10 & 9.50 & 8.30 & 0.00 & 0.00 \\ \hline \hline \end{tabular}  
* 0.13% of water corresponds to [PERSON]’s salt.  
\end{table}
Table 7: Thermogravimetry results for the composites immersed in a 1 M NH4 Cl solution.  
Figure 12: Modulus of rupture (**a**) and toughness (**b**) for the GRC composites immersed in a 1 M NH4 Cl solution.