## 3 Results and Discussion
### Characterization of Composites and Their Evolution by Aging
#### 3.1.2 Mechanical Behavior of the Aged GRC Composites  
The modulus of rupture (bending strength) values of the composites and their evolution with aging time are depicted in Figure 2. The values found ranged in 8-16 MPa, which are typical values found in the literature [29]. During SC, composite C obtained the highest value (12.79 MPa) and the pozzolanic-containing composites values were below 10 MPa (9.20 MPa for GFA60 and 9.48 MPa for GFA50+SSF10). However, the behavior  
Figure 1: Water absorption (**a**) and dry density (**b**) of the GRC composites. (SC, standard curing for 28 d at 20 °C; CS+Ag, 28 d SC plus aging for 28 d at 55 °C; Acc, short curing for 7 d at 20 °C plus Acc for 21 d at 55 °C).  
was very different for the composites that underwent Acc. Composite C had values under 10 MPa due to fiber deterioration (see the following subsections), whereas the composites containing pozzolans developed a very good cementing matrix and had significantly increased bending strength [17]: GFA60 with 14.95 MPa and GFA50+SSF10 with 13.44 MPa. This behavior demonstrated that the most important contribution of the pozzolanic reaction was achieved by increasing curing temperature. For the aging process (SC+Ag), the contribution of pozzolans was much more significant because the cementing matrix development was more intense during the ageing process: GFA60 with 16.67 MPa and GFA50+SSF10 with 16.92 MPa.  
The density of composite C increased with aging (Figure 1), but its modulus of rupture did not (Figure 2). For the pozzolanic composites, an increase in both density and strength took place with aging. This means that increasing density was not the key to strength development for the C composite because fiber deterioration occurred. For the pozzolan composites, fiber integrity was maintained, and increasing density favored an increase in mechanical properties.  
Figure 3 shows the toughness of the studied composites. For SC (28 days at 20 \({}^{\circ}\)C), composite C obtained a significant toughness value (1.35 J), which was only exceeded by pozzolanic composite GFA50+SSF10 (1.48 J). During the acceleration and aging processes, the toughness for C drastically dropped, but toughness was maintained for the pozzolanic composites.  
Figure 2: Modulus of rupture (bending strength) of the GRC composites. (SC, standard curing for 28 d at 20 \({}^{\circ}\)C; CS+Ag, 28 d SC plus aging for 28 d at 55 \({}^{\circ}\)C; Acc, short curing for 7 d at 20 \({}^{\circ}\)C plus Acc for 21 d at 55 \({}^{\circ}\)C).  
The micrographs in Figure 4 show the state of the AR fibers in the different composites and for various curing/aging conditions. The fiber surface deterioration in the C composite after curing is evident, with deterioration corresponding to sizing loss (Figure 4a). This behavior was previously reported by [PERSON] et al. [30]. Fiber deterioration increases with the aging process (pitting on the fiber surface) and the mass loss of filaments is quite evident (Figure 4b). Figure 4c,d show the state of the fibers in the pozzolan-containing composites after aging: good fiber condition is observed. There is no evidence for pitting and the accumulation of cementing hydration products on the filament surface appears in the pozzolan composites [8].