The effect of key parameters on the mechanical response of artificially cemented iron ore tailings for dry stacking purposes

Abstract

Regulations prohibiting the construction of new tailings dams using the upstream method and requiring the closure of the existing ones have been recently introduced in Brazil. This scenario demands the sought for alternatives to manage both the previously disposed tailings as well as the upcoming generated mining residues. Fortunately, advances in dewatering technologies have enabled the tailings’ dried disposal in stacks having hundreds of meters rather than the traditional slurry deposition. Eventually, a cement material can be incorporated into the tailings before the stacking aiming to enhance the overall material’s performance, permitting the construction of higher and more inclined piles. In this regard,the present study evaluates the effect of key variables on the stiffness and strength of compacted iron ore tailings-cement blends. Specifically, the effect of the following variables was statistically evaluated through a full factorial design set: dry unit weight (17, 18, and 19 kN/m³), amount of cement (1, 3, and 5%), curing period (7, 28, and 90 days) and cement type (pozzolana Portland cement and high early strength Portland cement). The results have shown that all the main factors, and most of the second-order interactions, were significant in altering both the strength and stiffness of the studied mixtures, with a highlight to the amount of cement, curing time, and dry density. The type of cement, in turn, has exerted a marginal influence. As well, both responses could be successfully correlated to the adjusted porosity/cement index via power-type functions.