Impact of anhydrite proportion in a calcium sulfoaluminate cement and Portland cement blend

Calcium sulfoaluminate (CSA) cement and ordinary Portland cement (OPC) blends are innovative binders. In comparison with OPC, these mixtures can reduce the environmental impact of cement production as well as increase the hardening speed. This article deals with the effects of calcium sulfate (anhydrite) percentage on hydration mechanisms, compressive strength and dimensional stability of binders containing 40% OPC. Calcium sulfate quantity is an essential parameter that can be used to control the hardening speed and dimensional stability. Mortars with 6.5% and 10% anhydrite present moderate compressive strength and expansion, whereas higher compressive strength and expansion are obtained with blends containing 17% and 20.5% anhydrite. These anhydrite proportions slow down the OPC and CSA clinker hydration kinetics but increase the ettringite proportion and stability.