## 3 Results
### Carbon Sequestration  
The thermogravimetry (TG) and DTG results of carbonated LFS with varying water-solid ratios and water contents are presented in Figure 7. The DTG results reveal that the mass loss peak between 400 and 800 \({}^{\circ}\)C represents the decomposition peak of CaCO\({}_{3}\). By employing Equations (2) and (3), the rate of mass loss over the temperature range can be used to calculate the carbon sequestration rate, as demonstrated in Figure 7a. It is observed  
Figure 6: The effects of different water–solid ratios and water content on the compressive strength of the samples. that the peak carbon sequestration rate of carbonated LFS increases with the water-solid ratio, in contrast to the result of compressive strength presented in Figure 7b. Although a higher water-solid ratio results in increased porosity, leading to lower densification and strength, these pores facilitate greater penetration of CO2 during the curing process. The carbon sequestration rate of LFS samples, characterized by a 0.35 water-solid ratio and 8% water content, amounts to 21.72%, indicating that each ton of LFS can effectively absorb and fix approximately 217.2 kg of CO2. This is much higher than the average carbon sequestration rate value of 15% proposed by researchers [19]. From the TG plot, it can be inferred that the carbonated LFS with a higher water-solid ratio is less influenced by the water content, suggesting that an increase in pore space mitigates the adverse effects of water on CO2 diffusion. The carbonated LFS exhibits an increasing then decreasing trend of the carbon sequestration rate with respect to water content, which is consistent with the compressive strength results presented in Figure 6. The current findings imply that maintaining an adequate water supply is crucial to ensure proper dissolution and solidification of CO2, yet an excessive increase in water content beyond a certain threshold potentially leads to adverse effects on CO2. In order to observe the distribution of water in samples with different water contents, the center of samples with a water-solid ratio of 0.3 and different water contents was cut to obtain a profile, and phenolphthalein powder was evenly sprayed on the profile. The LFS, a highly alkaline substance, would show color in the presence of water, as shown in the upper part of Figure 8. The sample with 0% water content did not show color due to the absence of water, which proved the feasibility of the test method. The increase in water content was observed to be accompanied by a progressively more pronounced coloration of the specimen's cut surface. Figure 7: (**a**) Carbon sequestration rate of carbonated LFS with different water–solid ratios and different water contents; (**b**) TG and DTG results of carbonated LFS with 0.25 water–solid ratio; (**c**) TG and DTG results of carbonated LFS with 0.3 water–solid ratio; (**d**) TG and DTG results of carbonated LFS with 0.35 water–solid ratio. After carbonation, the sample was uniformly covered with standard phenolphthalein solution on the central profile to indicate the carbonation depth, as shown in the bottom part of Figure 8. The sample with 16% water content has a darker color before carbonation and almost covers the whole sample. After carbonation, it was found that the sample also showed a darker color in the phenolphthalein solution, indicating that the degree of carbonation of the sample was small. This was because the excessive water content led to the hindered diffusion of CO2 during the carbonation process. With the decrease in water content, the color of the sample before carbonation became lighter and lighter. This proves that the moisture inside and outside the sample was reduced, and the resistance of CO2 diffusion was reduced. So when the water content was lower, the depth of carbonation would increase. Samples with 0% to 7% water content were fully carbonated to the inside.