Infiltration tests on a granite/bentonite mixture: Influence of water salinity

A series of infiltration tests on a 70% / 30% granite/bentonite mixture compacted at a dry density of 1.70 g/cm3 are reported and analysed. This mixture is proposed as backfill material in the Swedish concept for radioactive waste disposal. The tests have been carried out at laboratory temperature for different periods of time, between 10 and 100 days, and with two kinds of infiltration water, to check the influence of the salinity on the hydration behaviour. The water intake has been measured during the tests, and the distributions of water content, dry density and soluble salts of the material have been determined at the end of the tests. It has become patent the difficulty in accurately measuring these parameters in such heterogeneous materials. The influence of the permeant salinity on the intrinsic permeability of the material has been highlighted, as well as the swelling capacity of this mixture. The ionic species distribution depends on the kind of infiltration water and the duration of the test. Dissolution, advection and diffusion are the mechanisms identified.