Effect of the alkaline solution concentration on swelling performance of MX80 granular bentonite

Abstract

The influence of alkaline solution on swelling performance of granular bentonite is one of the significant factors that must be considered in the design of deep geological repository for disposing the high-level nuclear waste (HLW). In this paper, the effect of alkaline solution concentration on the swelling performance of compacted granular and powdered MX80 bentonite specimens were investigated by the swelling strain and swelling pressure tests, together with X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. Tests results showed that the swelling strain and swelling pressure of compacted granular MX80 bentonite increased by 2.6% and 7.6%, respectively, when the alkaline solution concentration changed from 0 to 0.1 mol/L. With increasing the concentration from 0.1 mol/L, the swelling strain and swelling pressure decreased significantly. When the alkaline solution concentration changed from 0 to 1.0 mol/L, the swelling strain and swelling pressure of the granular bentonite decreased by 35.1% and 41.6%. Observed XRD and SEM results showed that effect of the alkaline solution on bentonites led to a decline in montmorillonite content, and the large layered structure was dissolved into small layered structures and particles, which caused the decline in the swelling performance of granular MX80 bentonite.

Keywords:

• MX80 granular bentonite
• alkaline solution
• swelling performance
• microscopic mechanism

Data availability statement

The data that support the findings of this study are available from the corresponding author, De’an Sun, upon reasonable request.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was supported by the National Natural Science Foundation of China [Grant Nos. 42077229 and 41962014].