Effect of brine on swelling pressure of MX-80 bentonite and bentonite-sand mixture

Abstract of the technical paper/presentation presented at:
Clay Conference 2017 – The 7th International Conference on Clays in Natural and Engineered Barriers for Radioactive Waste Confinement
September 24–27, 2017

Prepared by:
G. Su, T.S. Nguyen, K. Lange, J. Brown, Z. Li
Canadian Nuclear Safety Commission
R.W.I. Brachman, M.S. Hosney, R.K. Rowe, A. Aickel, A. Baral

Abstract

A laboratory program has been developed to investigate the hydro-mechanical behaviour of MX-80 bentonite using brine prepared to represent the mean measured salinity concentrations from the host rock of the proposed deep geological repository in southern Ontario. The MX-80 bentonite is a reference bentonite for the buffer and seals and for a 70:30 bentonite/sand mixture that is proposed as the primary shaft seal for deep geological repositories for radioactive waste management. The abstract presents the effect of brine on the swelling pressure of the MX-80 bentonite and a 70:30 bentonite/sand mixture at different initial dry densities, which is compared with swelling pressures measured on the bentonite and the bentonite/sand mixture hydrated with deionized water. The measured results show that the swelling pressure of the particular MX-80 bentonite and bentonite/sand mixture when hydrated with brine model water is suppressed by high pore water salinity. This suggests that the effect of brine on bentonite behaviour should be taken into account for the buffer and seal design and safety assessment for both proposed deep geological repositories in Canada.

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