Thermodynamic data calculation for iron phases in sulfoaluminate cementitious materials prepared using solid wastes

The preparation of sulfoaluminate cementitious materials (SCM) is a promising way to massively utilize solid wastes. Iron phases are significant in SCM system but the thermodynamic data of some key minerals, such as 6CaO·Al2O3·2Fe2O3 (C6AF2) and 6CaO·2Al2O3·Fe2O3 (C6A2F), are missing, which greatly hinders the SCM optimization in a theoretical way. This work, for the first time, calculated the standard formation enthalpy, Gibbs free energy of formation, entropy and molar heat capacity for C6AF2 and C6A2F and lowered the errors to the least with the reference of C4AF data in the literature. By building the function diagram of Gibbs free energy changes with temperature for the basic iron phase formation reactions with the obtained thermodynamic data, it is proved that the formation likeliness of C6AF2 is higher than that of C6A2F, as is accordant to the literatures and verifies the correctness of obtained data. This work provides a good theoretical foundation to optimize SCM mineral system and to study relevant mechanism deeply.