Enhancing Reactivity of EAF Slag Based Ferrite-Rich Cement Clinker

The cement industry is working towards CO₂ cuts in clinker production, and ferrite-rich cement could be a solution. When compared to OPC cement, ferrite-rich cement requires less calcium, lower clinkering temperature and enables valorization of iron rich residues to a higher extent. Here, we utilize a novel Electric Arc Furnace (EAF) slag originating from new direct reduced iron ore (DRI) process route used in steel manufacture. The DRI process is an emerging low CO₂ production pathway that employs hydrogen in the direct reduction of iron ore. This new process route is intended to replace conventional blast furnaces in some parts of the world in the near future. In this study, 18.9% of this slag was used as the clinker feedstock (with other materials) with the aim to increase the ferrite phase (26.4 wt.%) in the clinker. The clinkering was done at 1400 ºC and the clinker was rapidly cooled, the phase composition of the clinker was analysed through X-ray diffraction. Iron rich phases in cement, such as ferrite (also known as brownmillerite), typically have poor hydraulic properties, to enhance their hydration, triisopropanolamine (TIPA) at two different dosages (low and high) were added in the cement and hydrated. The effect of this dosages on the ferrite hydration were then studied via isothermal calorimetry, X-ray diffraction (XRD), and thermogravimetry analysis (TGA). Results shows the potential of valorising this slag as a feedstock in cement clinker, and the reactivity of the increased ferrite phase can be improved with the addition of TIPA during hydration.