Preparation of red mud-based geopolymer materials from MSWI fly ash and red mud by mechanical activation

A novel method to activate red mud was proposed in this study. Municipal solid waste incineration fly ash (MSWIFA) and red mud were utilized to prepare red mud-based geopolymer materials (RGM). The hydration characteristics of RGM were studied by X-ray diffraction, scanning electronic microscopy, and Fourier transform infrared spectroscopy. The long-term stability and physical properties of RGM were tested by freeze-thaw cycle, European Community Bureau reference (BCR) and unconfined compressive strength (UCS) tests. Results showed that mechanical activation can not only effectively activate red mud, but also effectively improve the reaction of MSWIFA and red mud. When 14% sodium silicate was added to the binder, the UCS reached 12.75 MPa at 28 days. In the RGM, aluminosilicate was effectively activated by mechanical activation and reacted with calcium ion to form complex hydration products. The activator reacts adequately with activated aluminum to form a high-strength geopolymer. The freeze-thaw cycles and BCR test results also showed that the RGM had long-term stability and the characteristics satisfied the requirements of MU10 fly ash bricks. This study demonstrated that RGM may be utilized in cement composites.