Swelling Characteristics and Permeability of Bentonite-Based Materials Immersed in Various Solutions

Abstract

Chemical alterations of bentonite are critical factors for the ultra-long-term stabilization of barriers and backfill in radioactive waste disposal. The chemical alterations may deteriorate the properties of bentonite-based materials. However, experimental studies on the effects of chemical alterations on the swelling characteristics and permeability of bentonite-based materials have not been investigated extensively. In this study, the effects of chemical factors on the swelling properties and permeability of bentonite-based materials were clarified based on one-dimensional swelling-pressure, hydraulic conductivity, X-ray powder diffraction patterns, and element mapping images. From the analytical and experimental results, a small amount of K⁺, Fe³⁺, and Mg²⁺ can significantly deteriorate the swelling characteristic and permeability of bentonite-based materials in geological disposal (i.e., cause a decrease in swelling-pressure and an increase in hydraulic conductivity). Therefore, we conclude that it is necessary to pay close attention to the existence of these cations.

 

This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Japan 71 (2022) 395–401.