ABSTRACT
In Japan, an engineered barrier system consisting both of bentonite and cementitious materials is presently being studied for a low level radioactive waste repository. Calcium leaching from the cementitious materials into bentonite materials is one of the main issues for discussing the degradation of the engineered barrier system over an extremely long service life. In this study, the mixing of sodium carbonate into bentonite materials was proposed so that the precipitation of calcium carbonate at the cement/bentonite interface was expected to improve the performance of the multiple engineered barrier system. The effect of the mixing of the sodium carbonate was investigated by immersion tests of composite specimens consisting of the cement paste and the bentonite. The experimental results revealed that the mixing of the sodium carbonate generated calcite at the interface and reduced the degradation of the cement paste due to the calcium leaching.
