Beyond Bauxite or Alumina: A Review of Alternative Alumina Rich Sources for Calcium-Sulfo Aluminate Cement Production

Calcium Sulfo-Aluminate (CSA) clinkers are predominantly tailored for specialized markets that require distinct properties such as accelerated strength development and shrinkage compensation, both of which are primarily associated with the presence of the ye’elimite phase. The commercial CSA clinkers constitute a high ye’elimite content from the use of raw materials such as pure alumina or bauxite, which is listed as a critical raw material by the European commission and therefore significantly increasing the production costs. This economic limitation renders CSA cement substantially more expensive than Ordinary Portland cement (OPC), thereby confining its use to small-scale application. These challenges may be addressed by exploring alternative alumina-rich industrial by-products or Al-rich residues characterized by Fe₂O₃ and SiO₂ contents below 5% and Al₂O₃ content above 60 %, which hold the potential to fully substitute pure alumina or bauxite. Therefore, maintaining the high ye’elimite content of the CSA clinkers without the use of pure alumina or bauxite. However, incorporating Al-rich residues from the aluminium industry may pose a risk to the human health during clinker production due to its high dioxin content of ~ 35 ng TEQ kg⁻¹, higher than the limit proposed by SINTEF of 10 ng TEQ kg⁻¹. Therefore, future research direction should focus on initially the degradation technologies for dioxin removal from the raw material followed by evaluating the feasibility of using Al-rich industrial residues as the sole source of alumina in CSA clinker production, aiming to optimize their processing and performance while minimizing reliance on pure alumina or bauxite.