## 3 Results and Discussion
### Microstructural Analysis
#### 3.4.2 TG-DTG Analyses  
Figure 10 presents the TG and DTG curves for Ref. and 15 vol% CS after 28 days of water curing, while Figures 11 and 12 show the TG and DTG curves for the same mixtures after 180 and 360 days of exposure to either water or a 5% magnesium sulfate (MgSO\({}_{4}\)) solution, respectively. Figure 10a shows that the total mass loss between 50 and 1000 \({}^{\circ}\)C was approximately 22.7% for Ref. in water and 19.9% for 15% CS in water, confirming a lower degree of hydration in the CS-blended cement at early ages. This fact is consistent with the lower initial reactivity of CS, which delays the formation of hydration products compared to a pure Portland cement. In the DTG curve (Figure 10b), the first endothermic peak located between 80 and 200 \({}^{\circ}\)C is associated with the dehydration of C-(A)-S-H gel, ettrinigite (E), and AFm phases, as reported by [PERSON] et al. [88]. The mass loss in this region was approximately 10.4% for Ref. W and 9.3% for 15% CS W, indicating that the CS-blended cement produces fewer early-age hydration products. This result corroborates the findings of [PERSON] et al. [41], who observed reduced chemically bound water and fixed-line contents were reported for cement blends containing 20% of CS at 28 days. The second peak, observed between 400 and 500 \({}^{\circ}\)C, is associated with the dihydroxy-lation of portlandite (Ca(OH)\({}_{2}\)) [89]. The mass loss within this range was approximately 3.6% for Ref. W and 3.3% for 15% CS W. Since CS has been reported to have a pozzolanic contribution at later ages [41], this portlandite reduction is instead associated with a slight dilution effect, in which there are less clinker particles available to react, and form portlandite [89]. The third peak, between 600 and 800 \({}^{\circ}\)C, is attributed to the decomposition of calcium carbonate (CaCO\({}_{3}\)), probably formed due to incipient carbonation during sample preparation. Figure 10: (a) TG curves and (b) DTG curves of the Ref. and 15% CS for 28 days of curing in water. Before exposure to the MgSO\({}_{4}\) solution. Compared to 28-day results, in Figure 11a,b, Ref. and 15% CS mixtures cured in water exhibit an increase in total mass loss, indicating continued hydration over time. Moreover, the difference between Ref. W and 15% CS W is significantly reduced, which confirms the pozzolanic contribution of CS at extended curing times. In the TG curve, Figure 11a, the total mass loss between 50 and 1000 \({}^{\circ}\)C reaches approximately 21.5% for Ref. W and 20.37% for 15% CS W, reducing the gap observed at 28 days. In the first peak observed in the 80-200 \({}^{\circ}\)C region, which corresponds to the dehydration of C-(A)-S-H gel and AFt/AFm phases [90], the mass loss values are approximately 9.73% for Ref. W and 9.39% for 15% CS W, reflecting a comparable degree of hydration in the CS-blended cement and Ref. W. Moreover, it is possible to observe for the second peak between 400 and 500 \({}^{\circ}\)C, which is associated with the dihydroxylation of portlandite (Ca(OH)\({}_{2}\)), that portlandite content is 17.52% lower for 15% CS W compared to Ref. W due to its partial consumption by the CS pozzolanic reaction, similar to the obtained by [PERSON] et al. [41] in their previous work. Finally, the peak between 600 and 800 \({}^{\circ}\)C associated with the decomposition of calcium carbonate (CaCO\({}_{3}\)) [88], was nearly identical for both pastes, suggesting carbonation during sample preparation. However, under MgSO\({}_{4}\) exposure, a significant difference emerges between Ref. Mg and 15% CS Mg. The intensity of the C-S-H related peak (a) in 15% CS Mg is notably reduced, which is attributed to the partial conversion of C-S-H into M-S-H due to magnesium-induced decalcification. Since M-S-H is non-cemetitious and dehydrates  
Figure 11: (a) TG curves and (b) DTG curves of the Ref. W and 15% CS W for 180 days exposure to magnesium sulphate.