Synthesis and properties of inorganic polymers (geopolymers) derived from Bayer process residue (red mud) and bauxite

Abstract

Well-reacted geopolymers with good compressive strengths (44–58 MPa) were formed from highly alkaline residue from red mud (the residue remaining after extraction of alumina from bauxite by the Bayer Process) without the addition of strength-promoting components, such as fly ash or ground slag, by adjusting the composition to an optimal SiO2/Al2O3 ratio of about 3 with silica fume. The formation of these geopolymers is extremely energy-efficient since thermal dehydroxylation of the red mud is not required. The environment of the Si and Al in the geopolymers was shown by 27Al and 29Si NMR spectroscopy to be consistent with reasonably well-reacted aluminosilicate materials, suggesting that the..