Effects of mass concentration and curing age on the mechanical properties and damage evolution of aeolian sand backfill

As the critical load-bearing structure in the management of open-pit mine goaf areas, the mechanical properties of cemented backfill material play a decisive role in strata stability. This study investigates the influence of solids mass concentration (a) and curing age (T) on the mechanical response and damage evolution of aeolian sand backfill material through uniaxial compression tests, acoustic emission (AE) monitoring, and scanning electron microscopy (SEM) experiments. The results demonstrate that both the uniaxial compressive strength and elastic modulus of the backfill increase linearly with mass concentration and exhibit an exponential enhancement with increasing curing age. At a = 80% and T = 28 d, he uniaxial compressive strength and elastic modulus reach the maximum values of 7.01 MPa and 0.18 GPa, respectively. The microstructure analysis reveals that higher mass concentrations promote the formation of hydration products, reduce porosity, and lead to a more compact structure. Acoustic emission signals indicate that high-a specimens accumulate more energy prior to failure, and crack propagation becomes more localized and abrupt, exhibiting typical brittle failure characteristics. Energy evolution analysis further demonstrates that, with increasing a, the elastic strain energy ratio rises from 53.25 to 67.19%, while the dissipated energy ratio declines from 46.75 to 32.81%, reflecting enhanced structural homogeneity and improved interfacial bonding within the backfill. The findings provide a theoretical foundation and experimental support for the engineering application of aeolian sand backfill materials in open-pit mining.