CALCIUM FERROALUMINATE CEMENTS MADE WITH RED MUD: SYNTHETIC ISSUES AND MECHANICAL PROPERTIES

The high alkali content in red mud is one of the main issues faced in preparing the cement clinker. In this paper, a calcium ferroaluminate (CFA) cement clinker with and without CaSO4 (C$) was prepared using over 24.2 wt. % of red mud. The effects of C$ on the formation of the CSA clinker minerals at different calcination temperatures and the mechanical properties of the cement clinker were investigated. The results indicate that Na2O from the red mud obviously reduced the content of the dominant phase C4A3$ in the CFA clinker. In contrast, the C4A3$ content in the clinker specimens increases with the increasing C$ content in the raw mixture. The optimal calcination temperature for the CFA cement clinker with C$ is 1175 degrees C, whose compressive strength reaches 40.0 MPa and 57.9 MPa at 1 d and 28 d, respectively. In addition, Na2O firstly reacts with sulfate to form Na2SO4, and secondly incorporates the C4A3$ phase to form a solid solution in the CFA clinkers. The finding is important to improve the application of red mud in the preparation of cement clinkers.