New insight on geosynthetic clay liner hydration: the key role of subsoils mineralogy

The hydration of a needle-punched, thermally treated and powdered bentonite-based geosynthetic clay liner (GCL) from four different subsoils was studied at optimum moisture content +2% under isothermal conditions. Contrary to the belief that GCL hydration was strongly dependent on the percentage of clay-sized particles present in the subsoils, it was shown in this investigation that this dependency cannot be generalised to all subsoil types as the presence of smectite in the subsoils can substantially impact GCL water uptake. Smectite content of the subsoil has been found to enhance its water retention capacity, and therefore the relative amount of water available in the subsoil for hydration of the GCL was strongly dependent on the amount of smectite available in the subsoil (i.e., GCL water absorption from smectite-rich soils is impeded). The hydration process from subsoils dominated by smectite mineralogy was governed by the vapour phase, whereaswhen the smectite content was very low or nil the hydration process involved both vapour and liquid phases if the subgrade was at a water content close to optimum.