Abstract: In order to solve the problem of poor flow and low strength of cemented ultra-fine tailings backfill ( CUTB), this paper investigated the improvement effect of superplasticizer ( SP) on the properties of CUTB such as rheology,strength and ultrasonic pulse velocity,and proposed a prediction model of yield stress based on the water content of flocculant. The results show that:① The yield stress and equivalent plastic viscosity decreased by 51. 3% and 37. 5%,respectively,when the SP content increased from 0 to 0. 04%. ② The proposed dynamic yield stress model considering the water content of floc is scientifically valid,and the maximum packing density and effective solids concentration are the main fine-scale factors affecting the yield stress of fresh CUTB. ③ SP can significantly improve the strength of CUTB. When the SP content was increased from 0 to 0. 04%,the 3,7,28 dstrengths were increased by 17. 7%,34. 0% and 28. 0%,respectively. ④ The optimal SP content was 0. 03%. The results of this paper provide a reference for the actual use of SP to improve the performance of CUTB in mines.

Key words: superplasticizer,ultra-fine tailings,dynamic yield stress,uniaxial compressive strength,ultrasonic pulse velocity