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

Abstract

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 °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.

Keywords

• red mud
• calcium ferroaluminate clinker
• calcium sulphate
• temperatures
• mechanical properties