Neutron (and X-ray) tomography for the study of granular and porous media

During the last few decades, a number of advanced experimental techniques have provided an unprecedented insight into the behaviour of geomaterials. A notable example are the so-called full-field techniques such as X-ray and neutron imaging, which allow the non-destructive characterisation of the 4D (3D+time) response of geomaterials undergoing hydro–chemo–thermo-mechanical loading. While x-ray tomography over the last decade became a pillar in the domain, neutron imaging remains a comparatively less known tool. The unique properties of a neutron beam, such as high sensitivity to hydrogen (e.g., water, hydrocarbons), high penetration into metals (allowing the imposition of extreme boundary conditions), and isotope sensitivity (e.g., D2O/H2O), make neutron imaging an interesting tool for experimental studies of granular and porous media. This contribution provides an overview of recent contributions in this domain. A particular focus is given to the potential of some recent developments, such as the combination with simultaneous x-rays, new contrast options and substantial improvements in spatial and temporal resolution.