CIEMAT Publications

Abstract

To improve the understanding of the homogenisation process of bentonite barriers for geological disposal of nuclear waste, in particular with regards to the filling of technological voids, tests were performed with compacted FEBEX bentonite samples hydrated under limited axial swelling. The samples were saturated from the top surface using the vapour transfer technique (imposing suction), or with deionised water injected from the bottom surface or from the gap on top. Hydration was slower with water vapour than liquid water. The final water content of the samples tested under suction 6 MPa was lower and not enough to allow sufficient bentonite swelling to close the gap. In contrast, the samples saturated under suction 0.5 MPa reached higher water contents and were able to fill the gap before the equilibrium water content had been reached. In the tests performed with liquid water supplied through the gap, the samples saturated faster because they were able to swell into the open void and the higher-permeability swollen bentonite took water quickly. The final water content was higher and the dry density lower towards the hydration surface. These gradients were more remarkable and persistent as hydration was faster