Mechanism of clay swelling in Villarlod molasse: a Swiss sandstone

Abstract

The characterization of swelling clays is important for diverse fields, including the field of conservation of built cultural heritage. Villarlod molasse, a building stone utilized frequently across Switzerland, is known to be damaged by swelling clays embedded in its matrix. In this study, the mechanism of how the clays lead to swelling in the stone itself is examined, and similar to previous studies, crystalline swelling is noted as the most likely source. A scaling factor linking X-ray diffraction (XRD) and dilatometric swelling experiments is calculated, and evidence for the existence of an initial monolayer of moisture in the embedded clays at ambient relative humidities is presented. A qualitative micromechanical model describing how the nonswelling stone matrix exerts a pressure on the clay layers, affecting their swelling behavior, is presented.