Factors affecting hydration of geosynthetic clay liners in landfill applications

The progression of hydration of Geosynthetic Clay liner (GCL) from underlying subsoil was studied for three GCL products under simulated landfill conditions, before and after being covered by municipal solid waste. GCL hydration is shown to be highly dependent on the GCL manufacturing techniques, the grain size distribution and initial moisture content of the subsoil. The hydration behaviour of the GCL was also affected by the exposure conditions in the landfill. Prior to waste placement, the composite liner may be exposed to daily and seasonal thermal cycles for a period of time (weeks to months). These cycles significantly suppressed the hydration of the GCLs and kept the equilibrium moisture content of the GCLs far less than what expected under isothermal conditions at room temperature (22°C). After waste placement, the GCL may experience elevated temperatures that occur during waste decomposition in municipal solid waste landfills. Results indicated that as the temperature increased (from 22 to 55°C), the final equilibrium moisture content decreased, from about 96% at room temperature to about 14% at 55°C. Moreover, the normal stress of 2 to 5 kPa was shown to induce an adequately high rate of hydration and the maximum equilibrium moisture content