Effect of alkaline solution on hydraulic and mechanical properties of MX80 granular bentonite

Abstract

Granular bentonite is commonly regarded as a preferred anti-seepage and plugging material for the joints in high-level radioactive waste (HLW) repository. This study investigated the swelling, compression, rebound and permeability properties of MX80 granular bentonite with alkaline solution (0–1.0 mol/L). Results showed that compared with the alkaline concentration, the final swelling strain, compression and rebound indexes were negligibly affected by the particle size distribution. The preconsolidation pressure and hydraulic conductivity increased with increasing the concentration. When concentration c < 0.3 mol/L, the hydraulic conductivity was less affected by alkaline solution. When c > 0.3 mol/L, large aggregates were dissolved and resulted in a higher hydraulic conductivity. Results of scanning electron microscope (SEM) and processed images showed that the complexity, roughness and the size of the pores increased as the concentration increased. The dissolution of montmorillonite affected the pore size distribution and the hydraulic and mechanical properties of granular bentonite.