Water retention properties and microstructure of bentonite pellets/powder mixture

In situ compacted MX80 powder/pellets mixture is one of the candidate sealing materials for deep underground repositories, not only because of its low permeability, high swelling capacity and high radionuclide retardation properties but also for operational advantages (lower compaction effort, reduced gaps between the rock and the seal). Once installed in the repository, these sealing materials will be subject to coupled hydro-mechanical loadings: hydration due to the infiltration of pore water from the natural barrier and mechanical confinement resulting from the engineered barriers. It is therefore essential to understand their behavior under such loadings when assessing the overall repository safety.