Utilisation of phosphogypsum for sulfate-rich belite sulfoaluminate cement production

Phosphogypsum is an industrial by-product from phosphoric acid production. In order to consume as much phosphogypsum as possible, sulfate-rich belite sulfoaluminate cements are produced by incorporating high amounts of phosphogypsum into the raw mix. The presence of sulfate in the clinker is in the form of anhydrite, in addition to calcium sulfoaluminate. The aim of this paper is to study the effect of anhydrite on cement properties and the hydration process. Experimental results indicate that burning at 1270°C for 30 min is suitable for clinker production. The presence of anhydrite can prolong the setting time and improve the compressive strength. Compared with natural gypsum, anhydrite in the clinkers can promote the formation of ettringite. Results also show that the incorporation of phosphogypsum in the production of sulfate-rich belite sulfoaluminate cement is a promising way to utilise phosphogypsum.