## 3 Results
### Pore Structure  
In order to investigate the distribution of pore structures within carbonated LFS samples with a water-solid ratio of 0.3 and varying water contents, a high-resolution three-dimensional X-ray microscope was employed to analyze the central region of the samples. Pore identification is achieved through grayscale threshold segmentation, wherein the lower density of water compared to solids enables direct pore recognition during analysis. The porosity can be determined by reconstructing the test results in three dimensions. Figure 12 illustrates the porosity distribution along the Z-axis direction for two-dimensional cross-sections of samples with different water contents. It is evident that most curves exhibit overall flatness, with only a few positions displaying significant fluctuations attributed to large pore size defects present in the original samples. However, these defects remain within acceptable limits and do not undermine the value of our findings. Furthermore, it was observed that all samples exhibited reduced porosity after carbonation compared to their  
Figure 11: EDS result of carbonated LFS with 7% water content. Figure 10: SEM images of carbonated LFS with (**a**) 6% water content; (**b**) 7% water content; (**c**) 8% water content. pre-carbonation state. This reduction in porosity correlates with changes in compressive strength, carbon sequestration rate, and physical phase content as discussed elsewhere in this paper. Notably, as the water content approaches 7%, higher degrees of carbonation lead to increased generation of calcium carbonate, which fills up pores and contributes to enhanced strength. The test results were reconstructed in three dimensions, classifying holes based on connectivity into open and closed categories. The rendered results are presented in Figure 13. The upper section of the figure illustrates cut sections of the samples with varying water contents, while the lower section showcases the three-dimensional rendering. In the lower half of the 3D rendering, only the original shape is displayed, whereas in the upper half, both open and closed pores are visible with a priority given to displaying closed pores. It can be observed that micropores are distributed throughout the specimen, while closed pores are predominantly concentrated in its central region. Following carbonation treatment, there was a significant increase in closed pores within the specimen. This phenomenon may be attributed to calcium carbonate production blocking connecting pores and leading to an increased formation of closed pores. Figure 12: Axial pore size distribution of carbonated LFS with different water contents. Figure 13: Cutaway and 3D rendering of 3D CT of specimens with (**a**) uncarbonated; (**b**) 6% water content; (**c**) 7% water content; (**d**) 8% water content. The results of total porosity, open porosity, and closed porosity obtained through calculation are presented in Table 2. In total, 98.71% of the pores in the uncarbonated specimen are classified as open pores (Figure 13a), which facilitates favorable conditions for CO2 diffusion during the carbonation process. The variation in water content shows a similar trend between open porosity and total porosity, indicating that carbonation generates calcium carbonate that fills most of the open pores, enhancing overall compactness but reducing pore connectivity. Closed pores consistently increase with increasing water content. Notably, specimens with 8% water content exhibit higher levels of closed pores compared to those with 7% water content; however, they show lower levels of carbonation. This observation suggests that higher-water-content specimens possess more bridging water between particles and result in calcium carbonate deposition within particle gaps, leading to increased formation of closed pores. Consequently, this impedes CO2 diffusion pathways and affects later-stage carbonation progress.