## 3 Results and Discussion
### Microscopic Test Analysis  
Figure 10 illustrates the effects of temperature and humidity on the microstructure of carbonation-cured specimens. With an increasing temperature (Figure 10a,d,g), the nucleation and growth of calcite crystals around shield much particles accelerate, effectively filling harmful pores. However, exceeding the critical temperature (Figure 10g) causes crystal coarsening, generating new pores and cracks [50]. As humidity rises (Figure 10g-i), the inhibited enrichment of alkaline ions on the surface reduces the crystal size, alleviating carbonation-induced volume expansion. Nevertheless, excessive humidity (Figure 10i) compromises the pore-filling capacity of calcite and diminishes structural densification. All experimental groups followed similar trends, with Group G5 (Figure 10e) demonstrating optimal calcite pore-filling effects due to its ideal temperature-humidity conditions. [PERSON] et al. proposed that carbonation in alkali-activated slag paste occurs directly within the C-A-S-H gel [51]. Additionally, based on the thermal analysis results from [PERSON] et al. 's thermogravimetric tests on alkali-activated slag pastes, the differences in thermal decomposition behavior between G5 and G7 (exhibiting the largest performance variations in the study) were attributed to three characteristic stages: (1) structural water removal from the C-A-S-H gel in the 120-300 \({}^{\circ}\)C range, (2) C-A-S-H gel network depolymerization in the 250-600 \({}^{\circ}\)C range, and (3) calcite (CaCO\({}_{3}\)) decomposition in the 650-900 \({}^{\circ}\)C range(Figure 11) [52]. The G7 specimen demonstrated more intense mass loss rates throughout the thermal degradation process, with a higher calcite characteristic decomposition peak intensity than G5, confirming that high-temperature and low-humidity conditions significantly promote carbonation product formation. Quantitative analysis of the Table 4 data reveals higher mass loss percentages for G5 during both C-A-S-H structural water desorption and gel network decomposition stages, while demonstrating an inverse trend during calcite decomposition. This phenomenon is attributed to the densified calcite filling layer formed under 20 \({}^{\circ}\)C--70% RH conditions, which effectively inhibits CO\({}_{2}\) inward diffusion by refining harmful pore structures, thereby maintaining a stable alkaline environment for continuous C-A-S-H gel formation. Conversely, high-temperature and low-humidity conditions accelerate carbonation kinetics, where the crystallization-induced expansion stresses from excessive calcite generation cause pore coarsening. Concurrent carbonation-enhanced alkaline environment degradation and pore water migration-driven alkaline ion surface enrichment synergistically deplete internal alkalinity, ultimately suppressing C-A-S-H gel production during later curing stages. [PERSON] et al. utilized sulfur and alkali EDS mapping to delineate the carbonation front, explicitly identifying the interface between carbonated and non-carbonated \begin{table}
\begin{tabular}{c c c c} \hline
**Group** & **120–300 \({}^{\circ}\)C** & **250–600 \({}^{\circ}\)C** & **650–900 \({}^{\circ}\)C** \\ \hline G5 & 1.781 & 3.97 & 8.199 \\ G7 & 1.599 & 3.685 & 10.927 \\ \hline \end{tabular}
\end{table} 
Table 4: Thermogravimetric losses (%) for different temperature intervals. Figure 11: The TG/DTG curves of G5 (20 \({}^{\circ}\)C, 70% RH) and G7 (30 \({}^{\circ}\)C, 60% RH). zones [53]. Based on these experimental findings, it is justified to extend their conceptual framework, as illustrated in Figure 12: the specimen's surface layer adjacent to the exposed face constitutes the fully carbonated zone; the region where pore solution pH has not reached dynamic equilibrium represents the active carbonation zone; and the area with stabilized pore solution pH corresponds to the non-carbonated zone.