Water vapour adsorption and desorption in GCLs

Super-saturated salt solutions are used to control relative humidity (RH) and to infer the hydration (water uptake and loss) behaviour of three needle-punched geosynthetic clay liners (GCLs) with respect to time under conditions of both free swell and 20 kPa applied stress. It is shown that RH and applied stress play a key role in the hydration behaviour with time when GCL specimens were in equilibrium with water vapour. It was also observed that water uptake and loss was affected by the bentonite form (powdered or granular) and mineralogy of the bentonite. However, the effect of GCL structure (i.e. difference in geotextiles and bonding of needle-punched fibres to the carrier geotextile) on their hydration behaviour for GCLs with similar form of bentonite was not significant for RH≤97.7%. The effect of GCL structure became more apparent at 100% RH (for all GCLs). The results presented in this study can be used to better assess the hydration of GCLs in field applications such as waste containment liners and cover systems at different RH and overburden stress conditions.