Survey of methods for the study of the bentonite microstructure and its relevance to hydration

The report is the result of a limited literature survey that focuses on methods for investigating the microstructure of water-saturated bentonite. Knowledge of the microstructure is important in order to assess the bentonite's functioning as a barrier material in, for example, the planned Finnish repository for spent nuclear fuel. The following analytical methods were identified as suitable for the study of the bentonite microstructure: X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), electrical resistivity measurements, mercury intrusion porosity (MIP), scanning/transmission electron microscopy (SEM/TEM), vibrational probe studies of water, surface area determination and nuclear magnetic resonance (NMR). The authors subjective conclusion is that a combination of NMR, SAXS and surface area determination offers reasonably good possibilities to study the bentonite microstructure.