A Literature Review on Studies of Bentonite Alteration by Cement-bentonite Interactions

Abstract

Bentonite is being considered as a candidate for buffer material in geological disposal systems for high-level radioactive wastes. In this study, the effect of cement-bentonite interactions on bentonite alteration was investigated by reviewing the literature on studies of cement-bentonite interactions. The major bentonite alteration by hyperalkaline fluids produced by the interaction of cementitious materials with groundwater includes cation exchange, montmorillonite dissolution, secondary mineral precipitation, and illitization. When the hyperalkaline leachate from the reaction of the cementitious material with the groundwater comes into contact with bentonite, montmorillonite, the main component of bentonite, is dissolved and a small amount of secondary minerals such as zeolite, calcium silicate hydrate, and calcite is produced. When montmorillonite is continuously dissolved, the physicochemical properties of bentonite may change, which may ultimately causes changes in bentonite performance as a buffer material such as adsorption capacity, swelling capacity, and hydraulic conductivity. In addition, the bentonite alteration is affected by various factors such as temperature, reaction period, pressure, composition of pore water, bentonite constituent minerals, chemical composition of montmorillonite, and types of interlayer cations. This study can be used as basic information for the long-term stability verification study of the buffer material in the geological disposal system for high-level radioactive wastes.

Analysis of the Water/Cement/Bentonite Ratio Used for Construction of Cut-Off Walls

“…Bentonite, a clay primarily composed of montmorillonite, is widely recognized as a crucial component in engineering barriers due to its favorable properties. It serves as a buffer material for various safety functions within these barriers [10][11][12]. One of its key attributes is its ability to expand when groundwater infiltrates from the surrounding bedrock, creating a low-permeability barrier [13].…”

A Review of the Influence of Sulfate and Sulfide on the Deep Geological Disposal of High-level Radioactive Waste

“…스웨덴 SKB(Swedish Nuclear Fuel and Waste Management Company)에서 개발한 KBS-3(SKB, 2010) 개념의 심층처분 방식은 방사성 핵종의 생태계 노출을 차단하기 위해 금속처분용기(canister), 완충재(buffer), 뒤 채움재(backfill)를 포함하는 공학적방벽 시스템(engineered barrier system)과 처분장 주변 기반암 및 지중환경을 포 함하는 천연방벽으로 구성된 다중방벽처분시스템(multibarrier disposal system)으로 이루어져 있다(Fig. 1) (Zheng et al, 2015;Goo et al, 2022). 금속처분용기(canister)는 환경에 피해를 주는 방사성물 질을 장기간 격리하도록 구리(Cu) 또는 주철(cast iron)로 제작된다 (Posiva, 2013a).…”