Formulations of sulfobelite cement through design of experiments

This paper reports on the use of design of experiments for the formulation of sulfobelite clinkers. Samples made of 30–70 wt.%C2S, 20–60 wt.%C4A3Š and 10–25 wt.%C4AF were formulated. The red mud generated from the Bayer process was used in some formulations as source of iron and aluminum. X-ray diffraction was used to define the high and low limits of phase compositions. Estimations of CO2 emissions were also conducted. Derived cements (5 wt.% gypsum) were cured, and the temperature of hydration, compressive strength and density were determined. The Rietveld refinement showed that the percentages of phases in the clinkers are close to the expected ones. The presence of C4A3Š is crucial to improve the mechanical strength at early ages. The use of red mud leads to the formation of C3A and then the derived cements show faster hydration. In addition, C2S is the major responsible for the generation of CO2 emissions.

► Design of experiments was shown to be a useful tool to formulate sulfobelite clinkers.
► Strength dependence on compositional changes was described by special cubic model.
► C4A3Š presented the highest influence on the compressive strength.