Briefing: Gypsum: prospects for recycling

The term gypsum is used to refer to three main compounds of calcium sulphate: anhydrite, hemihydrate and dihydrate; but it is most often used for the dihydrate. The two main industrial uses of these compounds are in cement and in plaster products. Cement producers use a blend of gypsum and anhydrite as a set controller. Plaster is made with hemihydrate. This material is used both for bagged plaster and also to feed the plasterboard production lines. The materials are available from both primary and secondary sources. Waste plasterboard is an increasingly important secondary source but there are a number of problems which limit the proportion of this material that can be used in plasterboard production. Research is therefore in progress to find other uses for it, such as low-strength concrete mixes.