Viscosity of Polymer-Modified Bentonite as a Hydraulic Performance Index

Polymer-modified bentonites have been introduced in recent years to improve the chemical compatibility and performance of hydraulic barrier systems (e.g., geosynthetic clay liners) permeated with aggressive leachates. Laboratory experiments were conducted using a rotational torque viscometer to determine the viscosity of pure polymer and polymer-bentonite mixtures in suspension with saline solutions. Viscosity depends on the polymer-to-bentonite ratio, ionic strength, and anion and cation species. The bentonite fraction controls viscosity at polymer-to-bentonite ratios radi about 5% by mass. Polymer fraction controls viscosity at ratios approaching 10%. Low viscosity is interpreted to reflect a coiled polymer conformation, less effective hydrogel formation, and less effective bridging between polymer and clay units. Ongoing research is establishing potential links between the viscosity of polymer-bentonite suspensions and hydraulic performance of polymer-modified barrier systems in aggressive permeant solutions.