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Nakabayashi, Ryo*; Elakneswaran, Y.*; Chino, Daisuke*; Sato, Tsutomu*; Yoneda, Tetsuro*; Oda, Chie; Kaneko, Katsuhiko*
no journal, ,
Flow-through dissolution experiment was carried out using compacted bentonite with hyperalkaline solutions. In-situ observation of bentonite during the experiment was concocted by using X-CT analysis. Time-dependence of secondary minerals formation inside the compacted bentonite during the experiment was analysed and quantified based on the observation. Geochemical modeling using a 1D reactive transport code was able to reproduct time-dependence of space-distribution of minerals in the bentonite and Si, Al concentrations in the output solutions.
Nakabayashi, Ryo*; Elakneswaran, Y.*; Chino, Daisuke*; Sato, Tsutomu*; Yoneda, Tetsuro*; Oda, Chie; Kaneko, Katsuhiko*
no journal, ,
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.
Nakabayashi, Ryo*; Elakneswaran, Y.*; Sato, Tsutomu*; Oda, Chie; Yoneda, Tetsuro*; Kaneko, Katsuhiko*
no journal, ,
The objective of this study is to develop a microstructural analysis method by X-ray CT to track the alteration process arising from bentonite and hyperalkaline fluid interactions as a function of time and to use these data to underpin a geochemical model of the alteration process. Advective alteration experiment of bentonite was performed at 80 
C (pH = 13.5 at 25 C) for 180 days and in-situ analysis by X-ray CT during the experiment was conducted. The geochemical reactive transport code PHREEQC was used to simulate the results of the experiments. Consequently, the formation of secondary minerals (analcime) in the bentonite could be confirmed by X-ray CT at different times and quantified by X-ray CT images analysis. The predicted time-dependency of volume of analcime by a geochemical reactive transport model became consistent with the results obtained by X-ray CT analysis, and the concentration of dissolved Si and Al in the output solution could be replicated.
Nakabayashi, Ryo*; Elakneswaran, Y.*; Sato, Tsutomu*; Otake, Tsubasa*; Oda, Chie; Yoneda, Tetsuro*; Kaneko, Katsuhiko*
no journal, ,
The current study developed developed an in situ microstructural analysis method using X-ray CT to track bentonite/hyperalkaline fluid interactions. An advective alteration experiment was conducted by reacting a compacted bentonite (0.3 Mg/m
) with a 0.3M NaOH solution at 80C for 180 days. No significant dissolution of montmorillonite in the bentonite was observed using X-ray CT, although the formation of secondary minerals could be quantified by X-ray CT. A geochemical modeling using the dissolution rate of montmorillonite obtained in a dispersed system did not fit the experimental data, but could provide a satisfactory match to that by changes to the reactive surface area and the inclusion of an empirical term to account for the saturation state of montmorillonite. This implies that there is difference in effective reactive surface area and effect of the saturation state on the dissolution rate between dispersed and compacted systems.
solution; The Effect of pH and C-S-H precipitationKijima, Tatsuya*; Nakabayashi, Ryo*; Elakneswaran, Y.*; Oda, Chie; Otake, Tsubasa*; Sato, Tsutomu*; Yoneda, Tetsuro*
no journal, ,
pH dependency of Montmorillonite dissolution rate in Ca-Cl-OH aqueous solution system was confirmed by conducting a flow-through type dissolution experiment. C-S-H formed depending on the experimental pH and concentration of Ca. The dissolution rate determined in the condition where C-S-H formed differed from the rates obtained in NaOH solutions.
Kakuda, Ayaka; Osone, Osamu*; Hiraki, Yoshihisa; Osugi, Takeshi; Sone, Tomoyuki; Kuroki, Ryoichiro; Kudo, Isamu*; Elakneswaran, Y.*; Sato, Tsutomu*
no journal, ,
no abstracts in English
Hiraki, Yoshihisa; Saito, Toshimitsu*; Kakuda, Ayaka; Osugi, Takeshi; Sone, Tomoyuki; Kuroki, Ryoichiro; Kudo, Isamu*; Elakneswaran, Y.*; Sato, Tsutomu*
no journal, ,
no abstracts in English
Hiraki, Yoshihisa; Kakuda, Ayaka; Saito, Toshimitsu*; Osugi, Takeshi; Sone, Tomoyuki; Kuroki, Ryoichiro; Elakneswaran, Y.*; Sato, Tsutomu*
no journal, ,
no abstracts in English
Sato, Tsutomu*; Islam, C.*; Elakneswaran, Y.*; Hiraki, Yoshihisa; Osugi, Takeshi; Sone, Tomoyuki; Kuroki, Ryoichiro; Provis, J.*
no journal, ,
no abstracts in English
Hiraki, Yoshihisa; Kakuda, Ayaka; Saito, Toshimitsu*; Sone, Tomoyuki; Elakneswaran, Y.*; Sato, Tsutomu*; Osugi, Takeshi; Kuroki, Ryoichiro
no journal, ,
no abstracts in English