Low-CO2 Ferrite-rich Belite Ye’elimite Cements

Promovendus/a: Rahul Roy

Promotor(en): Prof. dr. Yiannis Pontikes, De heer Tobias Hertel

This PhD dissertation focuses on developing an environmentally friendly alternative to traditional Portland cement, which is a major source of global CO₂ emissions, responsible for 7% of the CO₂ emissions worldwide in 2024. The study explores a new type of cement called ferrite-containing belite-ye’elimite sulfoaluminate cement, which can significantly reduce both carbon emissions and energy use during production. A key innovation of this work is the use of industrial by-products—mainly bauxite residue and salt slag—to replace the expensive and limited raw materials such as bauxite, typically used to make calcium sulfoaluminate (CSA) cement. These residues, rich in alumina and iron, allow for the production of CSA cement at lower temperatures and with improved environmental and economic performance. In these synthesized cements, over 35% of the raw materials in the cement come from bauxite residue, and alumina-rich salt-slag was successfully used to completely replace bauxite, increasing the strength-giving phases in the cement. This approach supports a circular economy by turning industrial waste into valuable resources while potentially creating synergies between the aluminum and cement industries. However, challenges remain. One key issue is that the iron-rich components in the cement (called ferrites) do not react quickly enough with water, which can reduce performance. The research investigates ways to improve this, such as adding sulfate minerals and chemical additives like triisopropanolamine (TIPA). The results show that finding the right balance of these additives is crucial to enhance early strength and overall performance.

Overall, this work demonstrates a promising route toward more sustainable and circular cement production by combining waste valorization, process innovation, and chemical optimization.