Volume changes of swelling clayey soils at microscopic scale level

International audienceIn order to understand the mechanisms involved in swelling and shrinkage, experimental research was carried out at the microscopic level using Environmental Scanning Electron Microscope (ESEM). This device was used for the observation at a small scale of two natural clays as powder subjected to wetting/drying cycles. The first clay is the Greek montmorillonite, an homogeneous montmorillonite, and the second clay is Romainville clay, an heterogeneous interstratified clay. From image and chemical analysis, their behaviours are analysed and a comparison based on their mineralogical composition is performed. The mineral composition of the clay plays a significant role. We show that the homogeneity of the clay and the presence of carbonates significantly modify the deformation response of the clay to the wetting- drying loading. The different observations also show an evolution which can be decomposed into two distinct and successive steps. The particle size can influence the evolution or the rate of deformatio