## 3 Results
### Durability of Cementitious Composites Incorporating SS-PCM
#### 3.2.2 Chemical Stability: Carbonation  
Carbonation of concrete is a natural phenomenon that occurs in the long term in the ambient air. However, it is a slow process in atmospheric conditions taking a few years to reach high carbonation depth in the ambient air. The accelerated carbonation in a chamber at 3% CO\({}_{2}\) (20 \({}^{\circ}\)C and 65%RH) allows to speed up the process while maintaining stable environmental conditions according to the PERFDUB test method [27]. Figure 15 shows the evolution of the mass loss of mortar samples (4 \(\times\) 4 \(\times\) 16 cm\({}^{3}\)) during the drying period at 45 \({}^{\circ}\)C before the carbonation test. The water loss is greater for mortars incorporating SS-PCM compared to the reference mortar. As seen before (Figure 13), the mass loss increases with SS-PCM content. This should be related to the high porosity of SS-PCM composites. After 14 days in 45 \({}^{\circ}\)C oven, the mortar samples were stabilized at 20 \({}^{\circ}\)C and 65% RH during 7 days (prior drying stage) [27]. They were then introduced into an accelerated carbonation chamber (3% CO\({}_{2}\), 20 \({}^{\circ}\)C and 65% RH). Figure 14: Drying shrinkage as a function of time. Figure 15: Mass loss of mortars over time in drying oven at 45 \({}^{\circ}\)C for 14 days. The Figure 16 shows images of mortar samples after 14, 28, 48 and 360 days of accelerated carbonation. The phenolphthalein indicator was sprayed on the cutted surface to determine the carbonation depth. Phenolphthalein turns to purple coloration in area of pH higher than 9, so the purple coloration was observed in non-carbonated areas. The colorless outer area (carbonated area) thickened over time, i.e., the carbonation depth increased over time for all the tested mortars. At 360 days, the mortars with SS-PCM are fully colorless (i.e., complete carbonated). Figure 16: Image of SS-PCM composite mortars (4 \(\times\) 4 cm\({}^{2}\)) carbonated at 3% CO\({}_{2}\) chamber (20 \({}^{\circ}\)C, 65% RH). Figure 17 shows the measurement of carbonation depth at 14, 28, 48 and 360 days for each mix-design mortar (M0, M5, M10 and M15). As seen in Figure 16, there was no carbonation at the beginning of accelerated carbonation (t = 0 day). Then, the carbonation depth at 14 days was observed and could be measured for all samples. The carbonation depth of all mix-design mortar increased over time. However, the carbonation kinetics of the reference mortar was slower compared to SS-PCM composite mortars. The carbonation kinetics increased with SS-PCM content. After 1 year of accelerated carbonation, the carbonation of mortars incorporating SS-PCM (M5, M10 and M15) was complete (\(\geq\)20 mm), while that of reference mortar reached 6.8 mm. The high kinetic of SS-PCM composite mortars in relation to the reference mortar was due to its higher and coarser porosity, promoting a high diffusion of CO\({}_{2}\) into the porous network. It should be noted that the high carbonation depth of mortars incorporating SS-PCM is partially due to the severe carbonation conditions in the accelerated chamber (3%CO\({}_{2}\)). In the real condition of use (building application), the carbonation kinetics in the atmospheric air was slower compared to the accelerated chamber. In fact, the Figure 18 shows the image of mortars carbonated for 360 days at atmospheric air chamber and accelerated carbonation chamber (3% CO\({}_{2}\)). The SS-PCM composite mortars are fully carbonated in chamber at 3% CO\({}_{2}\) (\(\geq\)20 mm), unlike those in the air atmospheric chamber. In the atmospheric carbonation, the SS-PCM composite mortars show similar carbonation depth between 5 and 6 mm, while the reference mortar achieved only 1.7 mm in carbonation depth (Figure 19). This high carbonation rate of SS-PCM composite mortar could be an advantage in term of mechanical performance. Figure 20 shows an increase in mechanical strength with the carbonation rate.