Abstract
Sintering red mud (SRM) is an industrial alkaline waste residue generated from the sintering process in alumina production, which is often directly discarded and causes environmental issues. In this study, an innovative magnesium-modified wet carbonation method was proposed to convert sintering red mud to valuable calcium carbonate whiskers using CO2-containing flue gas. The effects of carbonation conditions including temperature, MgCl2 concentration, and duration on the composition, microstructure, and morphology of carbonated products were systematically investigated. It was found that a high whisker content of 60% with an aspect ratio of ∼6 could be obtained under the optimal conditions of 80 °C, 0.4 M MgCl2, and 2 h reaction time. Besides the formation of whiskers, amorphous aluminosilicate gel was also generated during SRM carbonation. The effects of the as-prepared whisker-rich materials as partial cement replacement on the mechanical properties of cement paste were evaluated with 5 wt% replacement, the 28 d compressive strength was significantly improved by 20.5% compared to the control specimen. The effective reinforcement was ascribed to the fibrous whiskers and enhanced interfacial bonding. This method enables high-value utilization of SRM waste and CO2 fixation, providing a green and low-cost approach to producing high-performance cementitious materials.
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