## 3 Results and Discussion
### Microstructure Analysis
#### 3.3.2 Pore Size Distribution  
Figure 12 shows the pore size distribution under different cement contents and initial water contents. The signal amplitude per unit mass is proportional to the number of pores in the samples, and the area under the curve is proportional to the volume of pores in the samples [50]. As shown in Figure 12a, the diameter, number, and volume of pores gradually reduced with the increasing cement content, attributed to the filling effect of hydration products on the pores [50]. As shown in Figure 12b, as the initial water content increased, the area under the curve and the pore size increased. This means that the rise in the initial water content leads to a loosening of the structure, explaining the decrease in strength. The pore diameter was mainly in the range of 1-300 nm for different soil-based CLSMs. The pore diameter of the cement-stabilized marine clay with metakaolin ranged from 5 to 1000 nm, as measured by MIP according to [PERSON], et al. [51]. This indicates that soil-based CLSMs with PCE are self-compacting materials from the perspective of the pore diameter distribution.  
Figure 11: \(T_{\rm 2 peak}\) under different cement contents and initial water contents.  
Figure 13 shows the distribution of the pore volume percentage in soil-based CLSMs under different cement contents and initial water contents. The pores in soil-based CLSMs are categorized into small pores (\(D\leq 10\) nm), mesopores (\(10\) nm \(<D\leq 50\) nm), macropores (\(50\) nm \(<D\leq 100\) nm), and extra-large pores (\(D\) > 100 nm) [50]. The 10 nm threshold distinguishes intra-aggregate and inter-aggregate pores in cement solidified clay [52]. Small pores represent intra-aggregate pores, while mesopores, macropores, and extra-large pores significantly different sizes of intra-aggregate pores [50]. As is seen in Figure 13a, an increase in the cement content led to a rise in the volume percentages of small and mesopores, while the volume percentages of extra-large pores and macropores gradually decreased. This reveals the micro-mechanisms underlying the strength increase with the higher cement content. The addition of PCE has little effect on the pore volume percentage distribution. The mesopores consistently dominated in volume for the soil-based CLSM. As the cement content increased from 8% to 25%, the volume percentage of the mesopores rose from 46% to 58.7%. This phenomenon is primarily attributed to the bonding and filling effects of cement hydration products, including C-S-H, C-A-H, and C-A-S-H, resulting in a gradual reduction in the mixture pore size and an increase in strength [36].  
Figure 12: Pore size distribution under different (**a**) cement contents and (**b**) initial water contents.  
Figure 13b demonstrates that a rise in the initial water content resulted in a notable increase in the volume percentage of extra-large pores, accompanied by a significant decrease in the volume percentages of small pores and mesopores. The volume percentage of macropores showed slight variation. This indicates that an increase in the volume percentage of extra-large pores and mesopores results in a decrease in the strength of soil-based CLSMs. Notably, at initial water contents of 62% and 80%, extra-large pores dominated. The volume percentages of extra-large pores at initial water contents of 80% and 38.8% were 47.9% and 17.4%, respectively. The former had 2.75 times more volume percentages of extra-large pores than the latter. The volume percentages of small pores at an initial water content of 80% were zero. According to [PERSON], et al. [53], the presence of numerous large pores in the sample is attributed to water being trapped within the pores, and the high initial water content inhibiting the formation of soil clusters.