# Research on Solidification Methods and Stabilization Mechanisms of Sulfate Saline Soils
## 5 Discussions and Conclusions
### Conclusions  
In this study, saline soils were stabilized by incorporating different proportions of lime, FA, and PAM binders and were subjected to UCS, splitting strength, freeze-thaw cycle tests, XRD, SEM, and TG tests. The major findings of this study are as follows:  
1. The addition of lime, FA, and PAM significantly increased the strength of saline soils. The UCS and splitting strength of stabilized saline soils gradually increased with an increase in binding material content. The best performance was obtained for lime, followed by FA, and the worst performance was obtained for PAM. The results of XRD, FTIR, SEM, and TG\(-\)DSC analyses showed that lime chemically solidified the soil by generating CaSO\({}_{4}\) and CaCO\({}_{3}\) as binding substances through ion exchange and carbonation.
2. The number of freeze-thaw cycles has a greater effect on the strength of stabilized soil; with an increase in the number of freeze-thaw cycles, the UCS and splitting residual value of stabilized soil decrease. SEM test results show that the internal structure of stabilized soil is more compact before freeze-thaw cycles. With an increase in the number of freeze-thaw cycles, the porosity of the stabilized soil increased, the contact between soil particles began to change, and the structure became loose; after 20 freeze-thaw cycles, a small amount of voids appeared in the lime-stabilized soil, a large crack appeared in the FA-stabilized soil, and the structure of the PAM-stabilized soil was destroyed.
3. Saline soils have a granular structure, and the contact mode is point to point. Time-stabilized soil changes the cementing substances from Ca(OH)\({}_{2}\) and Na\({}_{2}\)SO\({}_{4}\) to CaSO\({}_{4}\) and CaCO\({}_{3}\) through ion exchange and carbonation, which fill the pores between soil particles and change the contact between particles to face-to-face contact, thus enhancing the mechanical properties of saline soils.
4. XRD, SEM, FTIR, and TG analyses of FA-stabilized soil were consistent with the observed mechanical properties. The hydration of FA to form a C\(-\)(A)\(-\)S\(-\)H gel altered the microstructure of saline soils.  
This study mainly investigated the mechanical properties and frost resistance of stabilized soil with 1% sulfate content, and we did not investigate the shrinkage characteristics of stabilized soil, which can be further explored in future studies.  
Figure 15: SEM of FAS hydration at 7 d: (**a**) needle-like AFt and gel material; (**b**) short rod AFt and net gel material.  
**Author Contributions:** Conceptualization, S.L., R.Y. and Y.L.; methodology, S.L.; validation, S.L., Y.L. and Q.C.; formal analysis, Y.L.; investigation, R.Y.; data curation, Q.C.; writing--original draft preparation, S.L.; writing--review and editing, S.L.; visualization, J.S.; funding acquisition, Y.H. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the Scientific and Technological Research Programs in key Areas of Xinjiang Production and Construction Corps Science and technology Bureau, grant number [2023 AB013-01], Major Science and Technology Special Projects in Xinjiang Uygur Autonomous Region, grant number [2023A03004-04], and Xinjiang Uygur Autonomous Region Science and Technology Department, grant number [2023B03011-3].  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data are contained within the article.  
**Conflicts of Interest:** The authors declare no conflicts of interest.