Effect of CaO Sourced from CaCO(3) or CaSO(4) 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(3) or CaSO(4), on the phase formation and mineral composition of the IR-CSA clinker. Targeted samples were prepared with different proportions of CaCO(3) and CaSO(4) 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 Al(2)O(3) and Fe(2)O(3) tend to incorporate into C(4)A(3−x)F(x) [Formula: see text] with an increase in CaSO(4) as a CaO source, which leads to an increased content of C(4)A(3−x)F(x) [Formula: see text] but a decreased ferrite phase. In addition, clinkers prepared with CaSO(4) as a CaO source showed much higher x value in C(4)A(3−x)F(x) [Formula: see text] and higher compressive strength than clinker prepared with CaCO(3) as the sole CaO source. The crystal types of both C(4)A(3−x)F(x) [Formula: see text] and C(2)S 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.