Experimental study on time-dependent rheological properties and mechanical performance of cemented fine tailings backfill mixed with polypropylene fiber.

By preparing fine tailings slurry with different mass concentration and fiber content, the rheological parameters of slurry with different fiber content and curing time were tested. In addition, the influence law of fiber content and curing time on compressive strength was analyzed through the prepared fine tailings backfill samples, and the microstructure characteristics of fine tailings backfill were further studied. The results show that when the fiber content is 0.2 ~ 1.2%, the yield stress and plastic viscosity of the slurry increase with the increase of fiber content, and the thixotropy of the slurry also shows the same change characteristics. The bridge effect of fiber makes it easier for forming network structure, which increase the slurry rheology. When the curing time ranges from 0 h to 2.5 h, the increasing of curing time leads to the increasing trend of rheological parameters, and also increases the thixotropy of slurry. However, the increase of rheological parameters will continuously decrease when the curing time exceeds 1 h, indicating that the influence of curing time on yield stress and thixotropy will gradually weaken with the continuous extension of curing time. When the curing age increases from 3 to 56 days, the compressive strength of the fine tailings backfill increases with the curing age, but the increasing range of compressive strength decreases gradually. When the fiber content ranges from 0.2 to 1.2%, the compressive strength of backfill increases first and then decreases with the increase of fiber content, and reaches the maximum value when the fiber content is 0.6%. The extension of curing time reduces the generation of large-scale pore structure, which promotes the formation of more compact microstructure of backfill.