IEG 환경지질연구정보센터

(1)

지질공학│응용지질학

2011 추계지질과학연합학술발표회 초록집 333

Hydraulic conductivity of compacted bentonite permeated with hyperalkaline solutions : Preliminary results

Ha Ngoc Anh

^1,*

․Hyang-Sig Anh

¹

․Ho Young Jo

¹

․Yong-Kwon Koh

²

․Geon-Young Kim

²

1

Dept. of Earth and Environmental Sciences, Korea Univ., [email protected]

2

Korea Atomic Energy Research Institute

Compacted bentonite and cementitious materials have been being considered to use as buffer and backfill materials for a deep geological repository of high-level radioactive wastes in many countries. However, cementitous materials will be dissolved when contacted with groundwater for a long period, resulting in hyperalkaline leachate with elevated Ca concentration. The hyperalkaline leachate may alter bentonite properties (e.g., porosity and hydraulic conductivity) by dissolution and precipitation. The objective of this study was to evaluate the influence of hyperalkaline solutions on the alteration of bentonite properties (i.e., mineral component and hydraulic conductivity). Batch and hydraulic conductivity tests were conducted on Wyoming sodium bentonite using five alkaline solutions and 1M CaCl

2

solution.

The sodium bentonite was compacted at the dry density of approximately 1.0 g/cm

³

for the hydraulic conductivity tests. Chemical and physical properties (e.g., exchangeable cations, soluble salts, swelling index, and hydraulic conductivity) of bentonite after and before batch and hydraulic conductivity tests were measured. Bentonite and leachate obtained from batch and hydraulic conductivity tests were analyzed using XRD and ICP-AES, respectively to inves- tigate mineral dissolution and precipitation. Results of hydraulic conductivity tests showed that the hydraulic conductivity of compacted bentonite (k = 10

^-8

cm/s ~ 10

^-5

cm/s) for the NaCl solutions at pH>13 increased by approximately one to five orders of magnitude compared to that of compacted bentonite for DIwater. However, for the 0.02M Ca(OH)

2

solution having pH of 12, the hydraulic conductivity of compacted bentonite was similar to that of compacted bentonite for DI water (k ~ 10

^-10

cm/s) at a given test period (~3 months). Results of this study indicates that bentonite can be altered by interaction with the hyperalkaline solutions and extent of the influence can be affected by several factors (e.g., solution chemistry and interaction period).

IEG 환경지질연구정보센터

2011 추계지질과학연합학술발표회 초록집 333

Hydraulic conductivity of compacted bentonite permeated with hyperalkaline solutions : Preliminary results

Ha Ngoc Anh

․Hyang-Sig Anh

․Ho Young Jo

․Yong-Kwon Koh

․Geon-Young Kim

Dept. of Earth and Environmental Sciences, Korea Univ., [email protected]

Korea Atomic Energy Research Institute

solution.

The sodium bentonite was compacted at the dry density of approximately 1.0 g/cm

cm/s ~ 10

cm/s) for the NaCl solutions at pH>13 increased by approximately one to five orders of magnitude compared to that of compacted bentonite for DIwater. However, for the 0.02M Ca(OH)

solution having pH of 12, the hydraulic conductivity of compacted bentonite was similar to that of compacted bentonite for DI water (k ~ 10

cm/s) at a given test period (~3 months). Results of this study indicates that bentonite can be altered by interaction with the hyperalkaline solutions and extent of the influence can be affected by several factors (e.g., solution chemistry and interaction period).

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