The effects of eolian sand on the mechanical properties and pore structure of foam concrete under freeze–thaw cycles

Abstract Current research on eolian sand as a modifying material for foam concrete (FC) remains relatively limited, particularly the effects of eolian sand on the mechanical properties and pore structure of FC under freeze–thaw (F‐T) conditions are not yet clear. To address this, the study conducted uniaxial compression and acoustic emission (AE) tests on FC with varying sand–binder ratios (0, 0.25, 0.5, 0.75, 1) after F‐T cycles. Characterization was performed using nuclear magnetic resonance (NMR) to investigate the influence of the sand–binder ratio and the number of F‐T cycles on its mechanical properties, damage evolution, and pore structure. The results indicate that the stress–strain curve of eolian sand foam concrete (AS‐FC) under uniaxial compression exhibits four characteristic stages: compaction, elasticity, yielding, and plateau. When the sand–binder ratio is 0.25, the concrete demonstrates the highest peak strength and the lowest strength loss rate. After 80 F‐T cycles, its peak strength increased by 55.24% compared to the control group, while the strength loss rate decreased by 12.87%. F‐T cycles reduce the acoustic AE activity of AS‐FC and cause deterioration of the pore structure, significantly impairing its mechanical properties. The incorporation of an appropriate amount of eolian sand enhances the material's structure and effectively delays crack propagation, thereby reducing the cumulative ringing count. Meanwhile, it improves the pore structure, increases the proportion of pores in the 0.001–0.1 μm diameter range, and results in a more uniform pore distribution. However, an excessively high sand–binder ratio destabilizes the foam, resulting in pore structure degradation and stress concentration, which in turn accelerates crack propagation.