A Novel Model of Aggregate Gradation for Autoclaved Bricks from Tailings

Mining tailings as a raw material for preparing autoclaved bricks have attracted much attention. The tailings subjected to milling always have the characteristic of fine granularity. However, the proportion of the fine aggregates in autoclaved bricks was very low using the current gradation formula, which impeded the utilization of the tailings. In this work, a novel model of aggregate gradation for autoclaved bricks from tailings has been presented, which was established through the following steps: (1) 91 groups of autoclaved bricks with different aggregate gradations were prepared, with the proportion of the fine aggregates (−0.15 mm) in the range of 40% to 100%; and (2) the particle size distributions of the finest and coarsest aggregates in the high-strength region were fitted to establish the model. The proportion of the fine aggregates calculated by the model could increase significantly compared with that using the current formula. To verify the novel model, autoclaved bricks from iron ore tailings were prepared using the model, with their mechanical and freezing resistance properties meeting the requirement of the highest-strength level. It was observed by SEM that the autoclaved bricks had compact structures with a few small pores owing to the reasonable aggregate gradation.