Enhancing performance and structural integrity of cemented paste backfill: Rheological behavior, strength characteristics, and microstructural dynamics

In order to improve the mechanical properties of backfill, steel slag and straw fiber were used as materials to prepare backfill. The law of sand-cement ratio, mass concentration, steel slag content and straw fiber on strength and rheological parameters of backfill was analyzed by orthogonal test method, and the influence mechanism of steel slag content and straw fiber on physical properties of backfill was revealed. The results show that mass concentration exerts the most substantial impact on rheological parameters, emerging as a significant determinant. Moreover, the yield stress diminishes with escalating tailings-cement ratio, while it escalates with higher mass concentration, steel slag content and straw fiber content. Augmenting the tailings-cement ratio and steel slag content serves to impede the amplification effect of mass concentration on yield stress. Notably, the tailings-cement ratio emerges as the most influential factor affecting the uniaxial compressive strength (UCS) of the backfill, albeit the UCS diminishes with rising tailings-cement ratio. Elevating the mass concentration and steel slag content can counteract the debilitation caused by an increase in the tailings-cement ratio on the UCS of the backfill. Furthermore, heightened mass concentration can bolster the reinforcing impact of steel slag content on early UCS. The increase of tailings-cement ratio increases the size and range of the void inside the backfill, subsequently leading to the degradation of its macroscopic compressive strength. The adhesion between straw fiber and mortar matrix constitutes a pivotal factor in improving the integration of backfill, whereas steel slag contributes to improving the mechanical properties by enhancing the distribution of void structures within the backfill. This research not only offer data support and scientific guidance for the design of backfill ratio parameters but also facilitate the broader application of straw fiber and steel slag in mine backfilling operations.