Slag from decarbonised steel production suitable for cement
New slags produced in the melting furnace during decarbonised steel production via the direct reduction route are suitable as latent hydraulic binders in cement production. This is the result of the “SAVE CO2” research project.
The investigations, carried out on a laboratory and pilot plant scale, show that electric arc furnace slag produced from direct reduced iron (DRI) could replace conventional blast furnace slag with suitable process control and targeted chemical adjustment. For steel and cement production, this would mean a total potential saving of around two-thirds of current CO₂ emissions in the future, provided renewable energy is used.
Blast furnace slag has been used for decades in the cement industry as a high-quality, resource-efficient and climate-friendly secondary raw material. However, neither empirical data nor industrial applications existed for slags from DRI-based processes. Consequently, there was a lack of fundamental understanding of the chemical and mineralogical composition, vitrification, environmental compatibility and hydraulic activity of these new types of slag. The research project therefore focused on investigating how slag properties depend on variable feedstocks and process parameters, as well as assessing the technical and economic prerequisites for their full utilisation as a main component of cement.
David Algermissen, Head of the Secondary Raw Materials/Slag Metallurgy Department at FEhS – Institute for Building Materials Research, which coordinated the project: “The work with this excellent consortium was very successful. We were able to build up a foundation of knowledge regarding electric arc furnace slag, right through to pilot trials for the production of blast furnace slag 2.0 on a tonne scale and testing in cement and concrete. The next steps involve establishing the regulatory and legal framework so that the material can be brought to market promptly as soon as the slag is produced at thyssenkrupp.”
The “SAVE CO2” research project, launched in 2021 by thyssenkrupp Steel, Heidelberg Materials, the Institute for Metal Technologies at the University of Duisburg-Essen, Fraunhofer Umsicht and the FEhS Institute, was funded under the KlimPro-Industrie funding scheme by the Federal Ministry of Research, Technology and Space, as well as the European Union/NextGenerationEU, and managed by the DLR Project Management Agency.
Source: FEhS