Evolution of Pore Structure and Damage Mechanism Analysis of Cement–Silt-Modified Eolian Sand Under Freeze–Thaw Cycles

This paper explores how freeze–thaw cycles affect the mechanical properties and pore structure in cement–silt-modified eolian sand. The study addresses freeze–thaw durability issues for cold, arid region engineering. We tested samples with 5% and 8% cement content at a 3:7 silt-to-sand ratio using freeze–thaw cycling, unconfined compression tests, and an SEM. Gray relational analysis quantified pore–strength correlations. The results indicated that after 10 freeze–thaw cycles, the strength of the 5% cement content samples decreased by over 80%, while the strength of the 8% cement content samples decreased by approximately 25%. The total number of pores increased with the number of freeze–thaw cycles. The proportion of large pores also continued to rise. The pore shapes degraded from circular/elliptical to elongated. The pore orientation shifted from a concentrated distribution (90°~105°) to a more random dispersion. The proportions of large pores (with correlation coefficients exceeding 0.80) and extremely low abundance pores (with correlation coefficients exceeding 0.82) served as the primary microstructural parameters affecting strength loss. This research uncovered the freeze–thaw damage mechanism of cement–silt-modified eolian sand. It provides a theoretical foundation for material design in cold and arid region roadbed engineering and for enhancing the freeze–thaw resistance of modified materials.