Schwinden und Schüsseln von Estrichen – Auswertung des Schüsselns gemäß EN 13892-9

Shrinkage and curling of screeds – Evaluation of the curling according to EN 13892-9

Screeds are used to ensure the evenness and load distribution of floors. Particularly critical is the deformation caused by hydration and drying shrinkage which can lead to tension, cracks or even the lifting of the screed edges, the so-called curling. With DIN EN 13892-9:2019, a standardized method for the combined measurement of the change in length and the curling of screeds has been defined for the first time. There is a simple connection between the results of the change in length and the shrinkage elongation of the screed. In contrast, the standard does not yet describe any possibility for deriving a material-related, geometry-independent shrinkage deformation from curling measurement and consequently it is not considered in the evaluation.

This article provides a theoretical derivation for evaluating the curling which enables the calculation of the cross-sectional linear shrinkage difference. The derivation indicates that the Young's modulus is an important material property that influences results. The evaluation is applied to a real measurement of the dimensional stability of a cement screed mortar and discussed in the context of internal tensions and increased deformations under real site application.