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