Stabilisation of α′ dicalcium silicate in calcium sulfoaluminate clinker

Calcium sulfoaluminate cements are widely used as special cements and, because of their low specific carbon dioxide emissions relative to those of Portland cement, they have potential for use in general construction. However, their widespread application has been limited by the relatively high cost of aluminous raw materials. As part of a broad programme on the optimisation of these cements, the clinker mineralogy was reformulated to enhance the activity and strength contribution of the silicate phases. Preservation of the α′ dicalcium silicate phase to ambient is described in this paper. Commercially available raw materials and reagent-grade chemicals were used and clinker syntheses were conducted. Preservation of the α-belite phase to ambient temperature was achieved by a combination of chemical doping with control of the furnace atmosphere and fast cooling of the clinker. A clinker with α′-belite, ye'elimite and ferrite can be optimised to create a new generation of low-cost sulfoaluminate cements with improved performance and large potential energy savings relative to Portland cement.