Leaching behaviour of mixtures containing plaster of Paris and calcium sulphoaluminate clinker

The water resistance of plaster of Paris is limited due to the high solubility of calcium sulphate hemihydrate. In order to improve this resistance, calcium sulphoaluminate clinker was added to plaster at different contents: 30, 50, and 70%. Mortars were cast using these new binders and subjected to the Soxhlet extraction test. The presence of calcium sulphoaluminate clinker considerably reduced the quantity of sulphate extracted per day and after 5 days: from 78.9% to 89.1%. The analysis of microstructure showed the stability of ettringite during the leaching test and the refinement of the porosity.