Water uptake and water retention behaviour of bentonite-polymer geosynthetic clay liners

This study investigated the water uptake and water retention behaviour of bentonite-polymer (B-P) geosynthetic clay liners (GCLs) from subsoils. The B-P GCLs tested in this study contain linear polymer (B-LP) and crosslinked polymer (B-CP), and tests were also conducted with sodium bentonite (Na-B) GCLs as a control. Relative humidity controlling tests (e.g. 75%–98%) and subsoil hydration tests were used to investigate different water movement kinetics from subsoil to GCLs. Water retention behaviour of Na-B GCLs and B-P GCLs at wetting curve was characterised by chilled mirror hygrometer and filter paper tests. The results showed that the final water content of B-P GCLs was higher than that of Na-B GCLs under the same experimental conditions. Moreover, the water entry value for B-P GCLs were higher in comparison with Na-B GCLs, suggesting that polymer additives enhance the adsorption behaviour and capillary connections within macropores between the B-P composite. The Brunauer–Emmett–Teller tests suggest that different polymer types in B-P GCLs exhibited varying coverage mechanisms of the interfacial surface within the Na-B structure, which may lead to a different water uptake and water retention behaviour of B-P GCLs.