Alternative slags as supplementary cementitious materials

As cement production increases and the supply of suitable supplementary cementitious materials (SCMs) gets limited, new sources of SCMs need to be explored. Non-ferrous metallurgical (NFM) slags are of interest as SCMs. The composition of this type of slag is dominated by Fe and depending on the type of slag, the treatment process, and the raw materials, they may contain various minor elements. For use of NFM slags as SCMs, more knowledge is needed on their exact chemistry and reactivity, and on the hydration mechanism of the potential slag-cement system. In this project, the potential use of an industrial NFM slag as SCMs in Portland cement is therefore investigated. The investigation includes first a characterization of the slag in order to explore the chemical-mineralogical composition, glass content, average bulk composition of the glassy phase and the distribution of the minor elements in the slag. Second, the reactivity of the slag is assessed and compared to current SCMs, and third, the hydration mechanism of a cement-slag blend is investigated over time using stopped paste samples, characterizing both the solid and liquid phase. Based on the experimental data, a thermodynamic hydration model is developed.

In the project, additional focus is put on the influence of minor elements on slag reactivity using synthesized glasses resembling slag compositions doped with different minor elements. This serves to elucidate whether a general rule applies to the reactivity of slags dependent on the ionic size of the minor elements present.


Project Period

June 2018 - July 2021

Figure 1 – SEM image of a Portland cement with 30wt.% substitution by NFM slag hydrated for 31 days.

Project Leader


Malene Thostrup Pedersen

Funding Organization

Funded by industry and the EMPAPOSTDOCS-II programme

The EMPAPOSTDOCS-II programme has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement number 754364.



Conference Contributions

74th RILEM Annual Week & 40th Cement and Concrete Science Conference, August 31st – September 4th 2020 (Oral presentation)

5th International Workshop on "Mechanisms and modelling of waste-cement interactions", March 25th – March 27th 2019 (poster)