Dry Stacking of Filtered Iron Ore Tailings: Comparing On-Field Performance of Two Drying Methods

Stacking compacted filtered tailings has become an option to cope with the new Brazilian regulations while providing a safe disposal method for the tailings. It has become feasible due to recent developments in dewatering technologies. Still, the dewatering processes may need to be improved to attain acceptable moisture contents considering the on-field compactable range. Also, the filtered material's moisture content is highly influenced by the weather conditions, especially during the rainy season in the southeast of Brazil. Additives are a possible solution to accelerate moisture reduction. However, scientific studies in the technical literature still need to attest to the effectiveness of these methods to tailings, mainly on a full scale. Accordingly, the present research evaluates the performance of two additives to hasten filtered iron ore tailings drying for dry stacking purposes: commercially available quicklime and superabsorbent polymer. Also, undrained triaxial tests were conducted on specimens retrieved from on-field compacted layers to investigate the additive's influence on the tailings' mechanical behaviour. Initial confining pressures ranging from 100 to 600 kPa were used. The results have shown the inefficacy of the superabsorbent additives in boosting the drying process for on-field conditions and the efficiency of the quicklime in doing so. Furthermore, no substantial changes in the mechanical response were observed due to the insertion of quicklime. This highlights the novelty of the present study in the context of iron ore tailings management.