A Proposal for a 100 % Use of Bauxite Residue Towards Inorganic Polymer Mortar

Abstract

A new process is suggested in the present work turning bauxite residue (BR) into a ready-made mortar for the synthesis of inorganic polymers, effectively transforming the Bayer process into a zero-waste process. This was achieved by firing BR at 1100 °C which supports the formation of liquid phase and results after subsequent fast cooling in a semivitreous material. Based on thermodynamic calculations, the process was subsequently improved by adding minor quantities of C and silica to BR before firing which leads to the carbothermic reduction of ferric iron into ferrous iron; the new blends demonstrated an increase in the melt formation and eventually in the content of amorphous phase after solidification. The resulting material was activated using a K-silicate solution and was cured at 60 °C for 72 h. The synthesized materials were water insoluble and dense, demonstrating compressive strength exceeding 40 MPa for the silica-rich blend. These inorganic polymers can find applications in construction, such as pavement tiles or floor/roofing tiles. A possible implementation of the process to transform BR within the alumina refinery is also represented.