Synchrotron imaging of pore structure and drying behaviour in Toarcian argillite

Clay-rich rocks are commonly foreseen to be employed as hostrock for radioactive waste disposal due to their favourable properties, that is, high retention and low permeability. This study investigated the pore-related characteristics and drying pattern of Toarcian argillite using X-ray synchrotron imaging. Specimens at varying saturation levels exhibited consistent porosity across different radial locations, indicating limited drying heterogeneity which is crucial for sample preparation in laboratory material characterisation. Due to the imaging technique employed, most detected pores were on micron and submicron scales. Unconfined specimens showed greater porosity than those with axial confinement, and the presence of cracks inferred the influence of the swelling potential from the initial re-saturation process that disturbed the argillite integrity, especially in higher saturation conditions. The estimation of the air–water interface characteristic length was attempted based on theoretical insights from Laplace’s law. Computed tomography results suggest that the detected pores were mostly in the air phase, supporting a homogeneous drying pattern under imposed suctions. Correlation between porosity and suction further reinforced the hypothesis on this drying pattern. The findings offer critical insights, highlighting the significance of Synchrotron imaging techniques in understanding argillite behaviours in nuclear waste disposal environments.