Hydration of geosynthetic clay liners from clay subsoil under simulated field conditions

► Subsoil initial moisture contents, covering range of possible variations in the field, were shown to control the GCL hydration. ► Thermal cycles significantly suppressed the degree of hydration of GCL. ► Clay subsoil provided the least and slowest rate of GCL hydration. ► Results from this research indicate that the exposure conditions are the primary factors controlling the hydration of GCLs.