Abstract
In this paper, water retention curves of compacted Czech bentonite B75 measured by vapour equilibrium methods are presented. The controlled suction range was 3.29 MPa-286.7 MPa.
The changes in microstructure of compacted bentonite under free swelling was studied upon wetting and drying path. Mercury intrusion porosimetry (MIP) and environmental scanning electron microscope (ESEM) were used for the microstructure observation.
The MIP tests were performed on samples with two initial dry densities at three different suction levels. The ESEM observations were performed on the same samples, while the target relative humidity is imposed directly in ESEM chamber.
The ESEM and MIP results clarified the microstructural changes which bentonite undergoes during wetting and drying process. Interestingly, it appears that the aggregates are relatively insensitive to suction changes and significant proportion of wetting-induced swelling occurs on the macrostructure level.
We indirectly observed that the microstructure desaturated during drying and it thus appears that the common assumption of saturated microstructure may not be accurate.