## 1 Introduction
However, despite all these methods increasing the ultimate strength of the soils after F-T cycles compared to untreated soil, a common characteristic among all these stabilizers is a subsequent loss of strength after successive cycles compared to their initial strength before experiencing F-T cycles. This weakening suggests alterations to the embankment soil structure, accompanied by continuous ongoing volume changes during F-T cycles. This loss of strength, especially when coupled with volume changes, presents significant challenges for the stability of soil embankments and infrastructure. Another method to cope with the damages caused by F-T cycles is by using antifreeze materials in the soil. This approach prevents the soil moisture from freezing, thereby avoiding the development of ice lenses and the subsequent induced cracking, while maintaining the integrity of the compacted soil structure. Research on the impact of diverse antifreeze agents on soils is relatively scarce. Among these agents is monoethylene glycol (MEG), a type of ethylene glycol with various applications. While ethylene glycols are used in different fields, monoethylene glycolhas garnered significant attention from scientific communities for its applications, notably as an antifreeze agent [36; 37; 38]. However, a study has shown that MEG is not a favorable material for use as an antifreeze because it has adverse effects on clays, leading to a decrease in the compressive strength of the clay. The results of this study indicate that the strength and stiffness of soils contaminated with MEG are progressively diminished by the level of contamination [39]. Therefore, using it as an antifreeze agent in cold weather would not be feasible due to this effect. Consequently, our search for an alternative additive with antifreeze properties that does not compromise the strength of clay led us to magnesium chloride (MgCl\({}_{2}\)), a chemical salt. Some theoretical studies on the modeling of freeze-thaw effects on soil have demonstrated the impact of salt in water on lowering the freezing point within the modeling process, highlighting the significance of salt in the freeze-thaw process [40; 41]. Additionally, there have been studies examining the effects of a magnesium chloride (MgCl\({}_{2}\)) solution on the mechanical properties of soil as a stabilizer, which have shown improvements in soil engineering properties [42; 43; 44; 45]. However, the impact of MgCl\({}_{2}\) as an antifreeze agent on the properties of soils under freeze-thaw conditions remains unexplored. This study aims to explore how water-soluble magnesium chloride (MgCl\({}_{2}\)) impacts the physical and mechanical properties of clay soil under unfrozen conditions and after undergoing freeze-thaw cycles. The research incorporates various experiments, such as Atterberg limits, standard proctor compaction, unconfined compressive strength (UCS), and freeze-thaw (F-T) cycles, performed on soil specimens treated with different concentrations of MgCl\({}_{2}\) solution. To gain insights into the interaction of MgCl\({}_{2}\) solution with soil at the microstructural level, the research also includes microstructural analysis using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR).