## 3 Results and Discussion
### Microstructural Analysis
#### 3.4.2 TG-DTG Analyses
Finally, the last peak (labelled e), between 600 and 800 \({}^{\circ}\)C, attributed to the decomposition of calcium carbonate (CaCO\({}_{3}\)), is associated with the carbonation of both Ref. Mg and 15% CS Mg, during the sample preparation. Compared to 180-day results, as shown in Figure 12a,b, Ref. W and 15% CS W mixtures exhibit a greater total mass loss, indicating ongoing hydration. Moreover, no significant differences are observed between Ref. W and 15% CS W, confirming the sustained pozzolanic contribution of CS at extended curing times. In the TG curve, Figure 12a, the total mass loss between 50 and 1000 \({}^{\circ}\)C reaches approximately 24.5% for Ref. W and 23.12% for 15% CS W, thus maintaining the reduced gap previously observed at 180 days. In the first and second peak observed in the 80-200 \({}^{\circ}\)C region, that corresponds to the dehydration of C-(A)-S-H gel and AFt/AFm phases [90], the mass loss values are approximately 10.92% for Ref. W and 10.80% for 15% CS W, showing a continued comparable degree of hydration in the 15% CS W and Ref. W. In the second peak located between 400 and 500 \({}^{\circ}\)C, which is associated with the dihydroxylation of portlandite (Ca(OH)\({}_{2}\)), portlandite content is 22.33% lower for 15% CS W compared to Ref. W due to its partial consumption by the CS. 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] is equivalent for both samples, likely resulting from carbonation during sample preparation. However, under MgSO\({}_{4}\) exposure, as observed at 180 days, a clear difference persists between Ref. Mg and 15% CS Mg. The intensity of the peak (a) within the 50-100 \({}^{\circ}\)C region is slightly higher for Ref. Mg, which can be attributed to the presence of physically absorbed water within the matrix. It can be particularly from hydration products that can retain moisture in the pore structure. Among them, sulfate-containing phases such as gypsum form expansive crystals within pores and strongly retain physically bound water [96]. The intensity of the C-S-H-associated peak (labelled b) in the 15% CS Mg sample is higher than that in 15% CS W. This can be attributed to the formation of expansive sulfate phases, such as gypsum, thaumasite, and ettringite, which are known to precipitate within the pore structure during sulfate attack. These phases can retain significant amounts of physically absorbed water, which evaporates within this temperature range (typically 80-180 \({}^{\circ}\)C) and contributes to the apparent increase in DTG peak intensity. This behavior aligns with observations reported in previous works [92]. However, the Ref. Mg sample exhibits an even higher peak intensity in this region, indicating a greater accumulation of sulfate phases capable of retaining physically absorbed water. This is likely due to the higher availability of Ca(OH)\({}_{2}\) in the reference mix, which enhances the precipitation of gypsum and other sulfate compounds. Consequently, the larger quantity of physically absorbed water released in this temperature range further intensifies the DTG signal in Ref. Mg compared to 15% CS Mg. Subsequently, the third peak (labelled c) between 100 and 150 \({}^{\circ}\)C is more pronounced in Ref. Mg than in 15% CS Mg. As reported by [PERSON] et al. [93], and discussed above, this region reflects the overlapping dehydration of sulphate phases, and then the stronger intensity in Ref. Mg suggests a greater formation of gypsum, compared to 15% CS. A fourth peak (labelled d) observed between 300 and 410 \({}^{\circ}\)C is attributed to the dihydroxylation of brucite (Mg(OH)\({}_{2}\)) and early stages of M-S-H dehydration, as identified by [PERSON] et al. [93] and [PERSON] et al. [94], and explained before. Both Ref. Mg and 15% CS Mg exhibit noticeable intensities in this region, confirming the presence of brucite and M-S-H.