Abstract
The relative humidity (RH) and temperature of the environment were controlled to achieve the optimum conditions for curing bentonite-sand blocks before placing them in repository for the disposal of highly radioactive waste. These prepared blocks were stored in a climate chamber at a temperature of 20°C. A constant RH environment was created by oversaturating the sodium chloride (NaCl) solution (RH=75%) and the distilled water (RH=100%) in capped canisters. During the three-month-long curing process, the moisture content of these blocks was measured periodically by recording their weights and their volumetric shrinkage as measured by fixed dial indicators. The final moisture and dry density distributions were measured by sawing a block into 64 subsamples. The test results indicated that 100% is the optimum environmental RH for a block with 17% moisture content, based on the lowest decrease in moisture content (from 17.00% to 15.15%), less than 1% shrinkage strain, and without any visible surface cracks. The curing process also contributed to the moisture homogenization in the block as demonstrated by the decreased coefficient of variation of water content (from 5.35% to 1.07%).
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