Rheological Characterization of Tailing Pastes from Ore Mining

The rheological characterization of tailings from ore mining is crucial for investigating the risk of tailing dam breaks and optimizing pumping systems. The fundamental rheological parameter is the yield stress. Determining the rheological behavior of iron ore tailings remains challenging due to the presence of coarse and irregular particles over a wide range of sizes. The moisture content, or solid concentration, used in bench-scale testing of mining tailings can be an experimental limiting factor, as lower moisture levels and, consequently, higher solid concentrations, which may represent the in situ mining residue, often cannot be evaluated experimentally due to the inability of rheometers to operate within the stress range in which such material exists. We conduct several tests to measure the yield stress of a paste from a Brazilian ore mine. Such a material is highly complex, primarily due to its time dependence. Below the yield stress, it behaves elastically like a Kelvin-Voigh material. The time dependence is also related thixotropy or to material deposition, challenging its rheological characterization. An essential point of the present work is the discussion of different kinds of tests to measure the yield stress, pointing out their advantages and limitations. The yield stress values are obtained from flow curves and confirmed by two other tests: sinusoidal stress amplitude and strain-time measurements under fixed stress. We tested samples with water fraction ranging from 26.62% to 33.85%, resulting in a yield stress ranging from 13 Pa to 87 Pa.