An Evaluation study on the interaction of bentonite with highly alkaline porewater by using X-ray CT method; Dissolution rate of montmorillonite in compacted bentonite

Nakabayashi, Ryo*; Elakneswaran, Y.*; Chino, Daisuke*; Sato, Tsutomu*; Yoneda, Tetsuro*; Oda, Chie  ; Kaneko, Katsuhiko*

Flow-through dissolution experiment of compacted purified bentonite with highly alkaline solution was carried out in order to quantitatively understand the bentonite-cement interaction. A combined analysis with XRD and in situ-observation by using X-ray CT method were applied. A geochemical model simulation of the experiment considering kinetics of montmorillonite (the main component of bentonite) dissolution was carried out. From output of the simulation, it was found that (1) dissolution rate of montmorillonite in compacted system were slower than that in suspension system, (2) slowering rate resulted in invisible change in dry density of montmorillonite in the simulation, which was consistent with the experimental result, and (3) the reason for slowring rate could likely to be attributed to the constraint of reactive surface area of montmorillonite and the effect of saturation degree of powewater.