Effect of colloid filtration by bentonite barrier altered in alkalic conditions

not registered; Shibata, Masahiro ; Ueta, Shinzo*; not registered; Yui, Mikazu

In the construction of geological disposal repository for radioactive waste, cementitious material may be used, e.g. as a mechanical support for tunnel. Regarding such conditions, evaluation of bentonite buffer alteration by high-pH solution, which caused by groundwater-cementitious material interaction, is important. In this study, colloid filtration ability of bentonite buffer acceleratingly altered by high-pH solution was experimentally investigated. The compacted bentonite specimen were first hydrothermally treated at high-pH (pH 14 or pH 12.5, at 200C). Then the mineralogical alteration was identified by XRD, and colloid permeability test was conducted. In the case that the specimen was treated at pH 14, serious smectite dissolution and feldspar crystallization was observed, and colloid permeation was identified. From the results of this study, the importance of understanding of alteration behavior in the actual repository condition, and examinations of the colloid filtration ability of the alteration products are highlighted.