## 3 Results and Discussion
### Microstructure Analysis
#### 3.3.3 Porosity  
Figure 14 illustrates the influence of the cement content, initial water content, and curing time on the porosity \(\eta\) of soil-based CLSMs. Porosity exhibited a decrease with the increasing cement content and curing time, as shown in Figure 14a. Specifically, for samples with cement contents of 10%, 15%, 20%, and 25%, the porosities decreased by 2.1%, 17.7%, 23.7%, and 25.8%, respectively, compared to those with 8% cement content after 7 days of curing. The increase in the cement content and curing time led to more hydration products, filling the pores between clusters, thereby causing a reduction in porosity [52]. The porosity increased notably with a higher initial water content, as shown in Figure 14b. For samples with initial water contents of 46.5%, 62%, and 80%, the porosities increased by 18.6%, 22.2%, and 49.3%, respectively, compared to those with an initial water content of 38.8% after 7 days of curing. This increase in porosity may be attributed to a large amount of water being trapped in the soil particles of soil-based CLSMs. This reveals the mechanism of strength decrease from the perspective of porosity, resulting from an increase in the initial water content. The overall variation in the porosity of the soil-based CLSMs was minimal with the increasing curing time periods. This observation aligns with the findings for Metakaolin-cemented silty clay, where the porosity experienced a slight reduction, ranging from 0.66% to 1.13%, as the curing time period extended from 7 to 28 days [54].  
Figure 13: Pore volume percentage distribution under different (**a**) cement contents and (**b**) initial water contents.  
Additionally, in Figure 14a, the porosity of the sample without PCE with an 8% cement content (T1) decreased by 1.0% compared to the porosity of the sample incorporating PCE with an 8% cement content (T2). This reduction could be attributed to compaction effects during the preparation of the sample without PCE (T1). Consequently, soil-based CLSMs with PCE fulfill flow requirements without compromising density.  
Figure 15 illustrates the correlation between the unconfined compressive strength \(q_{\text{u}}\) and the porosity \(\eta\) of soil-based CLSMs under different curing time periods. The unconfined compressive strength of the soil-based CLSM consistently decreased with the increasing porosity under different curing time periods. This trend aligns with the observed decline in the unconfined compressive strength with the increasing porosity in cemented silty soil [55]. The \(q_{\text{u}}\) values for the samples without PCE (T1) are not represented in Figure 15. This is because the sample preparation method of T1 cannot be consistent with other samples containing PCE. The unconfined compressive strength \(q_{\text{u}}\) decreased exponentially with the rise in porosity \(\eta\) across various curing time periods, namely 7 days, 14 days, and 28 days. The best-fit curves demonstrated reasonable correlations. A clear exponential relationship is established between the porosity and unconfined compressive strength of soil-based CLSMs.  
Figure 14: Porosity under different curing times, (**a**) cement contents and (**b**) initial water contents.  
Figure 15: Variation in strength \(q_{\text{u}}\) with porosity \(\eta\) under different curing times.