Observation of water transport in compacted bentonite at elevated temperatures using X-ray tomography and image analysis

X-ray tomography and image analysis were applied to monitor the 4D (3D spatial with time) evolution of partial densities of bentonite and water in compacted Wyoming sodium bentonite under constant volume conditions at elevated temperatures. The experiments were conducted at four temperatures: 21 °C, 50 °C, 90 °C, and 130 °C, in a uniform temperature distribution. The study encompassed the validation of the method, and the applicability and limitations of the methodology for experiments at elevated temperatures were discussed. The results showed that the water uptake in bentonite is sensitive to temperature, and significant changes were observed between all the studied temperatures. Although the impact of temperature on water uptake has been observed before, this study obtained detailed 4D data, which is difficult to acquire using other methods. This methodology provides data for modelling the thermo-hydro-mechanical behaviour of compacted bentonite, which is required in the safety assessment of the geological final disposal of radioactive waste. • Quantitative 4D information about water content in compacted bentonite was acquired. • Measurements were based on X-ray tomography and image analysis. • The first time this methodology was applied at elevated temperatures. • Results can be utilised, for example, in the development of water transport models.