Opportunities for Use of Bauxite Residue in Supplementary Cementitious Materials 2020

Work on the use of bauxite residue in cement has been pursued for over 80 years with a number of successful technical studies, several large-scale initiatives and industrial usage in Portland Cement clinker production reinforcing the prospects of large-scale utilisation of bauxite residue in cementitious materials. The driving force behind the usage in the production of both Portland Cement and calcium sulfo aluminate /special cements is because of the iron and aluminium contents of the bauxite residue.

Meanwhile, and possibly having an even greater environmental impact in the long term, is the potential to use bauxite residue in supplementary cementitious materials. Considerable work has been undertaken on a laboratory/pilot scale exploring opportunities for bauxite residue as a filler in blended cements, sometimes for their pozzolanic activity but also to improve the mechanical properties in blended cement by other mechanisms such as optimising packing density or rheological characteristics. It has been observed at laboratory scale by several groups of researchers that bauxite residue as produced or after calcination, pure or mixed with other additives, may successfully replace clinker in blended cements at dosages between 10 and 20 wt%. If used as produced, this would have a significant impact on the cement industry CO2 emissions as the clinker production is responsible for 85 % of the total emissions in an integrated cement plant. Usage in clinker or blended cement productions will most likely occur in locations where there is a shortage of alternative conventional raw materials such as natural clays, bauxite and iron ore for the former and fly ash, blast furnace slag and ground limestone for the latter. In these situations, the use of bauxite residue would help the cement industry reach two of their most important strategic targets: resource efficiency, by replacing non-renewable iron and alumina sources, and CO2 emissions by minimising clinker production, the main CO2 origin in the cement manufacturing process.