To provide the cement composition excellent in ultralong-term durability with respect to proof stress performance, water cut-off performance, chemical stability, etc., and also to provide the shielding body which is capable of enclosing waste over an ultra-long period by using this cement composition and excellent in ultra-long-term durability with respect to proof stress performance, water cut-off performance, chemical stability, etc.
This cement composition comprises cement that contains 30 to 70 wt.% of pozzolan and preferably, further contains ≥40 wt.% of belite. Also, within this shielding body, waste is placed and a structure surrounding the waste consists of at least two layers, or preferably, at least four layers, wherein as the material of an inner layer(s) other than the outermost layer or other than the innermost and outermost layers of these layers, the cement composition is used. As a result, in this multilayer structure, for example, the hydration in the innermost layer directly adjacent to the waste is faster than that in the inner layer adjacent to the outside of the innermost layer and the hydration becomes faster in the direction from the inner layer adjacent to the outside of the innermost layer toward the inner layer adjacent to the inside of the outermost layer.
NAKANO TAKEHIRO
ISOHATA TATSUO
SUMITOMO OSAKA CEMENT CO LTD
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