Flow characteristics of paste tailings in surface disposal: the role of pyrite content

The flow characteristics of paste tailings (PT), including uncemented and lightly cemented paste tailings (UPT/LCPT), are critical for pipeline transport and surface paste disposal. These properties, particularly yield stress and viscosity, may be significantly affected by the presence of sulfide minerals like pyrite in tailings from hard rock mines. Pyrite's oxidative capacity alters the chemistry of mixtures, impacting their rheological behavior. However, comprehensive studies on the effects of pyrite on UPT/LCPT rheology are lacking, despite their importance for effective transport and disposal. This study experimentally assesses the influence of varying pyrite concentrations (0%, 5%, 15%, and 45%) on the rheological properties of UPT and LCPT, prepared with two binder types (PCI and Slag) and analyzed at room temperature (20 °C) over curing times (0, 20, 60, and 120 min). Key assessments included yield stress, viscosity, electrical conductivity, pH, zeta potential, and microstructural analysis. Results show that pyrite content substantially affects the rheological properties of UPT and LCPT. The rheological properties of UPT increased as pyrite concentration rose, with yield stress and viscosity rising in the order of 5%, 15%, and 45% pyrite content. In LCPT mixtures, yield stress increased steadily over time with increasing pyrite content, while viscosity increased with pyrite content but decreased over time. The results also show that pyrite content causes microstructural and chemical changes in fresh LCPT, particularly, changes related to interparticle forces and inhibition of cement hydration. These findings provide valuable insights for optimizing tailings management and advancing environmentally sustainable designs of LCPTs and UPTs.