Investigation of a supplementary cementitious material with three reactive components: the example of a carbonated mineral composite

The search for feasible low-carbon cement leads to an increase in the complexity of the mineralogy and chemistry of the binders. This study investigates a carbonated mineral composite as a potential SCM. It is composed of three major components: a filler (calcium carbonate), a pozzolanic component (Al-Si gel) and a potential hydraulic component (C2(A,F)). We examine the compatibility and contribution of each of these compounds as a supplementary cementitious material with the combined use of experimental methods and thermodynamic modelling. In particular, we demonstrate the early-age reactivity of this SCM in blended cement, validated by compressive strength on concrete (SAI = 1) at 28 days, although the reactivity test would imply a behavior similar to fly ash. The strength development is linked to an increased precipitation of AFm phases, and the contribution of the ferrite. The latter is confirmed through the direct observation of Fe-Si-hydrogarnet precipitation by SEM-EDS. The limitations of current analytical methods and their impact on the formulation of new ternary and quaternary blends are discussed.