Durability and damage evolution of cement-fly ash stabilized aeolian sand gravel under high-temperature curing and freeze-thaw cycles.

The scarcity of road construction materials in arid desert areas necessitates the utilization of local resources to ensure sustainable infrastructure development. This study investigates the durability and damage evolution of a semi-rigid base material composed of Cement-Fly Ash Stabilized Gravel with 100% aeolian sand replacement for fine aggregates (CFSAG). The mechanical performance was evaluated under simulated desert environments, including high-temperature curing (30 °C, 40 °C, and 50 °C) and freeze–thaw cycles in both water and 2% Na₂SO₄ solution. Additionally, Digital Image Correlation (DIC) technology was employed to characterize the microscopic strain fields and crack propagation patterns. The results indicate that elevated curing temperatures significantly enhance compressive strength, with 40 °C identified as the optimal condition for strength formation due to accelerated hydration. Conversely, resistance to freeze–thaw cycles decreased with higher aeolian sand content, and sulfate erosion accelerated surface spalling, causing the specimen mass to exhibit an "increase-then-decrease" trend. A strength evolution model was established based on freeze–thaw frequency and mix proportions, achieving a fitting accuracy of over 98%. Furthermore, DIC revealed that the strain and displacement variations during crack propagation in specimens exhibited a three-stage evolutionary pattern, with strain localization bands becoming more pronounced as compaction decreases. The study concludes that CFSAG is a feasible, durable, and eco-friendly solution for semi-rigid pavement bases in desert regions.