Low-suction water retention capacity of bentonite at high temperature

CIEMAT, Avd. Complutense 40, 28040 Madrid, Spain

^* Corresponding author: mv.villar@ciemat.es

Abstract

The study of the hydro-mechanical properties of compacted bentonite is relevant in the context of deep geological radioactive waste repositories, where bentonite will be used as buffer material between the waste canisters and the host rock and will be subjected to high temperatures and hydraulic gradients. This research aimed at determining the water retention curves of bentonite compacted at a repository-significant dry density (1.6 g/cm³) and at high temperatures (up to 100°C). This had been previously undertaken, but below suctions around 10 MPa the accurateness of the curves obtained was very low because of the methods and instruments used to determine them. To overcome this uncertainty, thermocouple psychrometers, which work properly in the low-suction range (below ~6 MPa), were tested. However, calibration showed that their performance was compromised when temperature rose above 60°C. Nevertheless, the results obtained were consistent with previous ones and allowed to confirm the decrease of water retention capacity with temperature. Additionally, it was checked that this decrease was more important for the low suctions.