Alkali-reduced Bauxite Residue as Novel SCM

• Published in: Nordic concrete research Vol. 63; no. 2; pp. 1 - 20
• Main Authors: Danner, Tobias, Sletnes, Malin, Justnes, Harald
• Format: Journal Article
• Language: English
• Published: Sciendo 01.12.2020
• Subjects: acetic acid; alkali reduction; bauxite residue; cement; pozzolan; red mud; sodium acetate
• ISSN: 2545-2819; 2545-2819
• DOI: 10.2478/ncr-2020-0015

Abstract Bauxite residue is a major waste stream available in large volumes globally that can cause risks to the surrounding environment (e.g. ecotoxicity) when disposed and stored by conventional methods. There is yet no large-scale application and the utilization as supplementary cementitious material might be the best way to re-use bauxite residue. The main obstacle for the utilization of bauxite residue in the construction industry is the high alkalinity. This paper presents first results of a study on alkali reduction of bauxite residue by acetic acid treatment and the potential application of this alkali reduced bauxite residue as pozzolan in cementitious binders. A process of alkali reduction is presented that can help solving waste management problems of alumina refineries by transforming bauxite residue to a less hazardous waste, while producing a reactive pozzolan and Na-acetate that can find application in the construction and infrastructure market. 90% alkalinity reduction of bauxite residue could be achieved by simply washing with diluted acetic acid. Alkali-reduced bauxite residue showed good pozzolanic reactivity regarding portlandite consumption, bound water and 28-day compressive strength of mortars with 20% replacement of OPC.