Geosynthetic Clay Liners (GCL's) are composites that combine geotextile outer layers with a core of low-permeability sodium bentonite clay. Bentonite is a natural sealant, which actuates (hydrates) on contact with water. GCL's are used as a replacement for compacted clay liners. Upon hydration, the bentonite in the GCL swells to form a low permeability clay liner with a hydraulic conductiivity of less than 5 x 10-9
cm/sec. As a result, GCL's can provide approximately the same hydraulic protection as one metre of compacted clay.
A GCL is a good choice as one of the components of a composite liner system in landfills or other critical containment systems. The GCL can reduce, and in some cases replace, the thick compacted clay liner normally required. Replacing this thick clay layer results in increased airspace; additional capacity that results in increased income for landfill operators. GCL’s are also good for seepage control in water containment, or in lightly contaminated water containment applications. GCL’s must be backfilled to provide confinement pressure in order to develop their full potential for impermeability.