## 3 Test Result Analysis
### Dry-Wet Cycle Test
#### 3.2.3 Effect of Sand Particle Content on Chloride Ion (0) Erosion Resistance of the CS-SS Samples  
The CS-SS samples with 5% and 15% sand particle content were subjected two dry-wet cycles, and the samples with different dry-wet cycles were taken out for an ion chromatography test. In the case of the results of the ion chromatography test, the larger the peak area of the element was, the greater the concentration of the ions [32]. Figure 11a,b showed that the peak area of Cl\({}^{-}\) in the CS-SS samples with 5% sand particle content was 0.47 \(\mu\)S-min after one dry-wet cycle in seawater and the peak area increased to 0.95 \(\mu\)S-min after two dry-wet cycles. It can be seen from Figure 12 and Table 5 that after separation by the ion chromatography column, the Cl\({}^{-}\) content also increased from 137.80 mg/L to 299.50 mg/L by increasing the number of dry-wet cycles from 1 to 2, an increase of 117.34%. As the number of dry-wet cycle increased the erosion of Cl\({}^{-}\) in the sample increased and the corresponding Friedel's salt generated increased, which was consistent with the XRD test results in Figure 10b, and the corresponding UCS of the samples decreased. In addition, compared with Figure 11b,c and Table 5, the peak area of Cl\({  
increase in sand particle content, and their anti-dry-wet cycle ability increases with an increase in the sand particle content and a decrease in the sand particle size. 2. The UCS of the CS-SS samples decreases sharply after two dry-wet cycles. The strength deterioration effect caused by the dry-wet cycle of the samples under seawater conditions is more remarkable than that under freshwater conditions. 3. The C-S-H gel produced by the hydration of cement in the CS-SS and the cemented soil-sand particle skeleton structure formed by the sand particles are the microphysical mechanism for the improvement of its UCS and resistance to the dry-wet cycle. The multiscale deterioration mechanism of the strength of the CS-SS during dry-wet cycles can be interpreted as follows: As the number of dry-wet cycles increases, short and dense microcracks appear at the microscale, destruction of the cementation interface is generated at the mesoscale, and the reduction of the UCS of the CS-SS is induced at the macroscale. 4. Through the SEM scanning electron microscope test, it was found that with the increase in the number of dry-wet cycles, the cementation interface between the particles in the sample was destroyed, and the cracks increased with the increase in the number of cycles, destroying the sample structure. Seawater is more corrosive to the sample, and the phenomenon of stratification and spalling between particles is more pronounced. The structure of the fine sand-solidified soil is relatively more complete and the strength loss is smaller, followed by medium sand and coarse sand. Through XRD mineral composition analysis, it was found that the freshwater/seawater dry-wet cycles reduce the hydration products in the sample, resulting in a decrease in the strength of the sample. Since the corrosive ions in seawater will destroy the hydration products and form Friedel's salt with poor cementation, which is unfavorable to the strength of the sample, the hydration products are greatly reduced after seawater circulation, so the strength reduction is greater. Conceptualization, S.L. ; Methodology, D.F. ; Formal analysis, D.F. ; Writing-original draft, Y.W. and D.F. ; Writing-review and editing, S.L. ; Visualization, Y.W. All authors have read and agreed to the published version of the manuscript. The authors are grateful to the National Natural Science Foundation of China (grant number 52078142), the Natural Science Foundation of Guangdong Province (grant number 2022A1515011047), and the Science and Technology Program of Guangzhou, China (grant number 202002030194) for their financial support. Not applicable. Informed Consent Statement: Informed consent was obtained from all subjects involved in the study. The data used to support the findings of this study are included in the article.