Effect of multiple-ion interaction on the swelling pressure of compacted Gaomiaozi (GMZ) bentonite

Hyperalkaline fluids produced by cementitious materials continue to penetrate into the barrier system of high-level radioactive waste repositories. The swelling pressure of compacted bentonite can be seriously deteriorated by multi-ion interaction. In this study, the swelling pressure tests were performed on compacted Gaomiaozi bentonite with a dry density of 1.70 g.cm(-3) to investigate multi-ion interaction on swelling pressure. Results show that K+ cations contained in the compound hyperalkaline test solution (CHTS) can cause the swelling pressure to present a continuously decreasing tendency through potassium exchange effect. The effect of the concentration of compound cations on the swelling pressure of compacted bentonite depends on the compound cation interaction, and a positive correlation exists between the swelling pressure and the concentration of compound cations. The effect of OH- anions on the swelling pressure of compacted bentonite is closely related to the compound cations contained in CHTS, which presents a multi-ion interaction. The investigation of the effect of multi-ion interaction in CHTS on the swelling pressure can establish a baseline for later comparison with hyperalkaline pore water obtained from field conditions.