Bauxite free iron rich calcium sulfoaluminate cement: Preparation, hydration and properties

Abstract

For the preparation of calcium sulfoaluminate (CSA) cement without bauxite, the iron rich CSA cement was prepared by the partial substitution of Al for Fe in C4A3s-. Besides, the hydration and properties of iron rich CSA cement were investigated. Raw meal proportioning shows that iron rich CSA cement clinker can be prepared without bauxite when the x value of C4A3-xFxs- exceeds 0.7. Results demonstrate that the iron rich CSA cement clinker can be prepared at 1175–1225 °C with the heat preservation time of 10 min. With the rise of Fe2O3 content in the raw meal, the C4A3s- content of iron rich CSA cement clinker lowers down, more C4AF and C2F forms, more c-C4A3s- forms at the expense of o-C4A3s-, and the crystal size of C4A3s- becomes smaller. For the iron rich CSA cement, the setting time is prolonged and the expansion rate lowers down with the rise of Fe2O3 content. For the compressive strengths, the iron rich CSA cements are lower than that of CSA cement at early hydration age. However, the compressive strength of iron rich CSA cement exceeds that of CSA cement at 90 d. Therefore, it is available to prepare bauxite-free iron rich CSA cement with high late age strength.