ABSTRACT
Bentonite buffer material in the geological disposal of high-level radioactive waste would be subjected to high temperatures and pressures for a long period, which may cause alteration through cementation and changes of swelling and permeability characteristics. In this study, bentonite ore was used to simulate the cemented buffer material, and effects of cementation on swelling and permeability properties were evaluated. As results, swelling pressure of undisturbed specimens was about half that of reconstituted specimens, while hydraulic conductivity was almost in the same order. To elucidate mechanism from microstructural viewpoint, SEM and XRD was utilized. SEM observations showed the undisturbed specimens had more complex structure at same dry density. XRD analysis indicated that undisturbed specimens had smaller montmorillonite basal spacing at same water content. Therefore, cementation may reduce permeability by complexity of structure, and inhibit water absorption and swelling of montmorillonite interlayers, resulting in almost no change in hydraulic conductivity.
