Characteristic mechanical and moisture values and shrinkage behaviour of calcium sulphate screeds

Mineral building materials are subject to changes in volume even without th e influence of external loads. The physical cause of such changes in volume is the change in water content needed to achieve a state of equilibrium wi th the ambient air moisture. In addition to these physical processes, which are determined to a great extent by the pore structure and equilibrium moi sture content of the building materials, the factors influencing the shrink age in, for example, cement-based building materials are extremely complex due to the superimposition of physical and chemical processes. In contrast, the shrinkage of products with calcium sulphate binders can, apart from ef fects in the initial stages, be attributed to purely physical processes [13 ]. Changes in length as a result of swelling and contraction were measured in five calcium-sulphate-based flow screeds. Not only these swelling/contra ction measurements but also various characteristic values of the strength a nd deformation behaviour as well as pore structure parameters and moisture parameters were determined in order to be able to provide a mathematical de scription of the drying and deformation behaviour of these screeds in furth er investigations.