Evaluation of a geosynthetic clay liner water retention curve using vapour equilibrium technique

The Vapour Equilibrium Technique (VET) has gained popularity as a reliable method for controlling relative humidity as well as vapour suction in various porous media. In this study, super-saturated salt solutions were used to control Relative Humidity (RH) and to infer the water retention curve for a needle punched geosynthetic clay liner with respect to time under free swell and 20 kPa applied stress. Results showed that GCL sample RH plays a key role in moisture absorption/desorption behaviour and equilibration time when RH is in equilibrium with suction. Water absorption isotherms for the bentonite component of GCL agreed well with literature data. It was also observed that the effect of applied stress on water retention was more pronounced at high relative humidity and corresponding low suction. The results presented in this paper can help improve the understanding the water retention behaviour of GCLs in field applications such as waste containment liners and cover systems.