Preparation of belite-sulfoaluminate cement with phosphate-rock acid-insoluble residue: Modification and influence of impurity ions on cement properties

•The impurity ions in the PAIR can promote the formation of mineral phase of B-CSA cement clinker.•The impurity ions in the PAIR can effectively activate the mineral phase of B-CSA cement clinker.•Impurity ions in the PAIR can effectively improve the strength development of B-CSA cement. In this study, one of the raw materials used to make the belite-sulfoaluminate (B-CSA) cement is the phosphate-rock acid-insoluble residue (PAIR). Herein, the effects of the impurity ions in the PAIR on the properties of B-CSA cement were investigated. The results show that the impurity ions in the PAIR can promote the formation of a large amount of clinker mineral phase below 1200 °C. This promoting effect decreases when the impurity ion content is too high. The impurity ions in the PAIR can activate the mineral phase of the cement clinker such that the contents of orthorhombic crystal form calcium sulfoaluminate, ɑ′ and ɑ crystal form dicalcium silicates reach 30.71 %, 21.57 % and 5.16 %, respectively. After the activation of the clinker mineral phase, mechanical properties of the cement were improved considerably within 28 days. Its compressive strength reached 67 Mpa, which is 15 Mpa higher than that of the unmodified cement (52 Mpa) of the same age.