Investigation of Drying‐Induced Shrinkage and Curling in Screeds

Abstract

Drying‐induced deformation due to shrinkage is a major cause of damage in screeds and the flooring applied on top. Such deformation involves both a permanent contraction of the screed layer and a temporary lifting of the screed edges, commonly referred to as curling. Although this behaviour is well known for cement‐based screeds, it can also occur in complex ternary‐bound and other dimension‐controlled screed mortars.

Here we investigate the drying‐induced deformation of an OPC based screed and of a dimension‐controlled, ternary bound screed mortar. Results of the combined measurements of shrinkage and curling in reference to EN 13892‐9 are reported, accompanied by tests aimed at characterizing the mortars and their drying properties. An analytical, diffusion‐based drying model is employed that enables a description of the time‐dependent drying process and the resulting deformation of the cement screed. Applying the model to the dimension‐controlled screed mortar indicates a much more complex expansion and shrinkage behaviour that appears to be heterogeneous across the layer thickness.