Abstract
Many Chinese aluminum enterprises now choose to mix sintering process red mud and Bayer process red mud in the proportion of 1:1 to form mixed red mud and then stockpile the mixed red mud in the open air. In this study, the strength characteristics and the mechanism behind cementation hardening of the mixed red mud were investigated from the aspects of microstructure and macromechanical properties under different dewatering times. It was found that many hydraulic cement minerals and active ingredients in the red mud undergo a series of hydration reactions and carbonization reactions during dewatering, forming cementing minerals, which finally results in a large increase in the cohesion. These reactions mainly complete in the first 70 days of dewatering. In addition, the influence of acid on the strength characteristics of mixed red mud was also studied. It was found that even though the mixed red mud is soaked in a high-concentration acid solution (2 mol/L) for a long period (60 day), its strength only decreases slightly. These findings can provide important references for the open-air storage of red mud and the analysis of stability of the stockpile.
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