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.