Synthesis and Mechanical Characterization of Iron Oxide Rich Sulfobelite Cements Prepared Using Bauxite Residue

Abstract

The bauxite residue (BR) is the solid waste of largest generation by the aluminum industry, with a generation estimated in 10 million ton/year in Brazil. Its high alkalinity demands elevated costs to store it safely. Due to the high content of Al2O3 and Fe2O3 in BR, the present study evaluated its application for the synthesis of iron rich sulfobelite clinkers. Because of its composition, the cement made with this clinker presents environmental (30% to 62% reduction of CO2-equivalent emission), economic and even technical advantages over Portland cements. Formulations containing: limestone, gypsum, BR and clay, were fired at 1230°C to synthesize the clinkers. Variations in BR and clay content were studied to obtain three formulations, F-15, F-18 and F-21, of different Al2O3/Fe2O3 ratio values. Cements containing more than 10.5 wt-% of BR achieved mechanical resistance comparable to Portland cements (CP-II-Z32 and CP-V-ARI) for 7 and 28 days of curing age.