Effect of CaO Sourced from CaCO or CaSO on Phase Formation and Mineral Composition of Iron-Rich Calcium Sulfoaluminate Clinker.

The performance of iron-rich calcium sulfoaluminate (IR-CSA) cement is greatly affected by mineral composition and mineral activity in the clinker. This study aims to identify the effect of CaO sources, either CaCO or CaSO, on the phase formation and mineral composition of the IR-CSA clinker. Targeted samples were prepared with different proportions of CaCO and CaSO as CaO sources at 1300 °C for 45 min. Multiple methods were used to identify the mineralogical conditions. The results indicate that the mineral composition and performance of the IR-CSA clinker could be optimized by adjusting the CaO source. Both AlO and FeO tend to incorporate into CAFS¯ with an increase in CaSO as a CaO source, which leads to an increased content of CAFS¯ but a decreased ferrite phase. In addition, clinkers prepared with CaSO as a CaO source showed much higher value in CAFS¯ and higher compressive strength than clinker prepared with CaCO as the sole CaO source. The crystal types of both CAFS¯ and CS were also affected, but showed different trends with the transition of the CaO source. The findings provide a possible method to produce IR-CSA cement at a low cost through cooperative utilization of waste gypsum and iron-bearing industrial solid wastes.