Effect of wet and dry cycles on lighter bentonite-polymer geosynthetic clay liners

This study evaluated the hydraulic conductivity (K) of lighter bentonite-polymer (B-P) geosynthetic clay liners (GCLs) subjected to wet-dry cycles which simulated seasonal conditions on a GCL installed in a landfill cover system. Lighter bentonite-polymer composite (B-P) GCLs are manufactured with a lower mass per unit area of sodium bentonite (Na-B) (approximately 2.9 kg/m(2)) than conventional Na-B GCLs (approximately >= 3.6 kg/m(2)) which can reduce the transportation and installation costs compared to conventional Na-B GCLs. Hydraulic conductivity tests on lighter B-P GCL and Na-B GCL were conducted with a synthetic soil porewater leachate to represent wet season conditions on a landfill cover. Between hydraulic conductivity tests, GCL samples were placed in sealed chambers with a relative humidity of 75% until the water content of the specimens decreased to 55%, which represented dry season conditions of a GCL under a geomembrane in a cover system. Slight increases of the hydraulic conductivity were measured for both the Na-B and lighter B-P GCLs. After 5 wet-dry cycles K of the Na-B GCL increased from 3.1 x 10(-12) m/s to 8.3 x 10(-12) m/s, and K of the lighter B-P GCL increased from 1.6 x 10(-12) m/s to 8.3 x 10(-12) m/s.