Optimising the Performance of Bentonite in Geosynthetic Clay Liners

Geosynthetic clay liners (GCLs), developed over the last quarter century, are innovative
composite matting comprising of bentonite with two covering geosynthetics. The three-layered (2:1)
clay mineral montmorillonite forms the dominant (approximately 75-90% by weight) clay mineral in
the bentonite that is used in its manufacture. Quantitative mineralogical analyses with an assessment
of the adsorbed cation regime need to be normally carried out as part of performance appraisal. The
mineralogical and geotechnical differences between the preferred sodium and the less effective
calcium montmorillonite are presented in the paper. The liners with its encapsulated high active clay
minerals depend on the water balance between the sealing element and the surrounding soil layers.
Assessment of long term hydraulic conductivities and clay-leachate compatibility assessment is also
deemed necessary and the derogatory factors affecting the performance of the bentonite in GCLs
placed in difficult construction and hostile chemical environments are discussed. The performance
specifications for GCLs are identified in this paper and the need to enhance its cation exchange
capacity with polymer treatment coupled with the need for factory prehydration of the untreated
sodium bentonite is emphasised.

Citation:
Wijeyesekera, D.C. (2006) ‘Optimising the Performance of Bentonite in Geosynthetic Clay Liners’ Proceedings of the AC&T, pp.124-129..