Preparation of special cements from red mud

Red mud from HINDALCO (Hindustan Aluminium Corporation) Industries Limited, Renukoot, India, contains significant quantities of alumina, iron oxide and silica. Presence of the said constituents makes it a suitable ingredient for the preparation of special cements. Preparation of three varieties of cements was investigated, namely: (a) aluminoferrite (C 4AF)-belite (β-C 2S) using lime + red mud + fly ash; (b) aluminoferrite-ferrite (C 2F)-aluminates (C 3A and C 12A 7) utilising lime + red mud + bauxite; and (c) sulfoaluminate (C 4A 3S̄)-aluminoferrite-ferrite using lime + red mud + bauxite + gypsum. The effects of composition (proportions of lime, red mud, fly ash, bauxite and gypsum), firing temperature and duration on the properties of cements produced were studied in detail. Cements made from lime + red mud + bauxite or lime + red mud + bauxite + gypsum exhibit strengths comparable or superior to ordinary Portland cement (OPC). On the other hand, those prepared using lime + red mud + fly ash did not have sufficient strength. Moreover, it was not possible to replace bauxite by fly ash (as a source of alumina) in any significant quantity. † † The following notation has been used, throughout the text: A: Al 2O 3, C: CaO, F: Fe 2O 3, H: H 2O, S: SiO 2, S̄: SO 3, T: TiO 2.