The Swelling experiment of altered bentonite by alkaline solutions

Ichige, Satoru*; Honda, Akira

Bentonite clay may be used as a barrier to retard the migration of radioactive species by sorption ability and low permeability. Also, the cemetitious material is envisaged as the structural and backfilling material in the vaults. The groundwater in contact with the cementitious material will be alkaline condition in the repository and this alkaline condition will affect the performance of the bentonite. Therefore, it is necessary to investigate the altered bentonite for estimating performance of the in disposal system. In this study, to investigate interaction of amount of montmorillonite and swelling power of altered bentonite, the swelling experiment of altered bentonite were carried out. The altered bentonite were made using synthetic cement leachates (pH=14) at high temperatures (160 deg). The block sample heated for 10 days and 17 days, and the powder sample heated for 7 days. Three samples were carried out swelling experiment and the amounts of montmorillonite were determined by Methylene Blue adsorption method. It was shown that swelling power and quantity of montmorillonit have dependence. The volumes of the block sample which heated for ten days increased in a swelling experiment slowly. The cementation that occurred by the process that making altered bentonite came loose slowly, and it seems that a sample swelled. It is for future work to investigate relation with swelling power and Amount of montmorillonite. Furthermore, it is to investigate quantity of montmorillonite which there is by cementation loosely.