A Study on the Mechanical Properties and Hydration Process of Slag Cemented Ultrafine Tailings Paste Backfill

Abstract

Paste backfill prepared with ultrafine tailings often faces difficulties in meeting engineering requirements. To address the challenge of using ultrafine tailings, this work utilized a slag cemented ultrafine tailings paste backfill (SCUPB) composed of slag, Portland cement, and desulfurized gypsum as the cementitious materials, with a binder–tailing ratio of 1:4 and a solid mass concentration of 60%. The fluidity and compressive strength of the SCUPB were tested at 3 days, 7 days, and 28 days, while the microstructure and hydration process of the SCUPB were studied by scanning electron microscopy and isothermal calorimetry. The results reveal that the fluidity of the SCUPB decreases with the increase in the slag content and increases with the decrease in the c/g ratio. SCUPB attains the highest early compressive strength with a slag content of 70% and a c/g ratio of 3:2 (with the cement content at 18% and the desulfurized gypsum content at 12%). In this slag–gypsum–cement system, the combined activation of the slag by the cement and desulfurized gypsum exhibits a higher early compressive strength. This work utilized ultrafine tailings to prepare paste backfill that meets the engineering requirements, achieving the effective utilization of ultrafine tailings in mine backfilling projects.