Lage-CO2 Ferriet-rijk Beliet Ye’elimiet Cementen

One of the pathways for decarbonizing the cement industry is the development of ferrite-containing belite-ye'elimite sulfoaluminate cements as a sustainable alternative to Portland cement (PC), whose production is associated with high energy consumption and accounts for approximately 4% of EU and 7% of global CO₂ emissions. The work focuses on the valorization of industrial residues, particularly bauxite residue (BR) and salt slag, as alternative sources of alumina for clinker production, which are traditionally obtained from scarce and costly raw materials such as bauxite. By incorporating over 35 wt% BR into the raw meal, clinkers with >30 wt% ferrite content were synthesized alongside ye'elimite and belite phases, enabling sintering at temperatures below 1300 °C. To fully eliminate the use of primary alumina sources, a salt-slag by-product (>60 wt% Al₂O₃) was employed, which increased the ye'elimite content up to 40 wt%, thereby enhancing early-age strength. The study underscores the potential for industrial symbiosis between the alumina/aluminum and cement industries, promoting waste valorization and resource efficiency. However, the limited reactivity of the high ferrite content in FR cements presents a key barrier to widespread application. To overcome this, the research investigates chemical activation strategies involving sulfate blending and the addition of triisopropanolamine (TIPA). It was found that while ferrite dissolves more rapidly without sulfate addition, such systems underperform in ettringite formation. Optimal sulfate dosing is therefore required to balance ferrite dissolution and maximize ettringite formation. Additionally, the effectiveness of TIPA in enhancing ferrite hydration is shown to depend strongly on the type of sulfate used, due to differences in dissolution kinetics between gypsum and anhydrite. Overall, this research contributes to the advancement of low-CO₂ binders with high clinker substitution potential, offering pathways for industrial-scale implementation through circular material use and targeted hydration optimization strategies.