In the radioactive waste disposal facility, sodium-type bentonite will be used as an artificial barrier material. They are expected to delay the infiltration of groundwater and fill the crack with the surrounding ground because they have high swelling performance. However, during the tens of thousands of years, the bentonite can be deteriorated and dissolved by the alkaline solution leached from the surrounding cement-based materials. Then, swelling performance of the bentonite may be lowered.

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... n order to solve this problem, we proposed a method to mix inorganic materials such as fly ash, silica fume, sodium carbonate and ground granulated blast-furnace slag. In this study, we investigated the effect of the mixing on the degradation of swelling performance of the bentonite by using specimens immersed in the saturated aqueous solution of Ca(OH) 2 or the distilled water. The experimental results revealed that the maximum swelling strain of the bentonite immersed in the saturated Ca(OH) 2 solution was improved by mixing of fly ash, silica fume, or sodium carbonate. On the other hand, the mixing of ground granulated blast-furnace slag reduced the maximum swelling strain because the specimens were not saturated by the solution.