Influence of the clay coating properties on the dilation behavior of sandstones

Long-time exposure on historical buildings can enhance significant differences in stone durability according to their intrinsic properties, structure and composition. This study aims to identify stone parameters inducing macroscopical behavior i.e. hygric dilation. The content, nature and properties of the clay coating of several Triassic siliceous sandstones were assessed. A special emphasis was put on cation exchange capacity and specific surface area measurements using different methods (BET, EGME and MBA). Hygric free swelling and mercury intrusion porosimetry measurements enabled the assessment of macroscale behavior and pore structure. Results showed very slight differences in clay coating properties and clay content. However, hygric free swelling coefficient values were well correlated to clay minerals when the clay content was taken into account together with the total specific surface area of the clay coating. Clay intracrystalline swelling had a relevant impact on the macroscale behavior of the stones submitted to relative humidity cycles.

Research Highlights
► Contribution of sustainable sandstones for restoration work.
► Specific surface area measurements using three methods.
► Dilations under RH cycles were correlated to clay minerals, content and nature.
► Clay coating plasticity influenced dilation and reversibility.