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The rheological characteristics of purified bentonite suspensions as a function of exchangeable cation (Ca2+,NH4+,Li+)$({\rm{C}}{{\rm{a}}^{2 + }},{\rm{NH}}_4^ + ,\;{\rm{L}}{{\rm{i}}^ + })$ are studied at three different clay concentrations (40 gL−1, 60 gL−1, 80 gL−1). A Herschel-Bulkley model is used to determine rheological parameters such as yield value, consistency and fluidification index. The flow curves are typical for shear thinning fluids but differ on two points; presence of yield stress and/or thixotropy. The Li suspensions are not yield stress fluid, and the thixotropy is weakly expressed only for the 80 gL−1 suspension. On the contrary, Ca-clay suspension flow curves always present yield stress and a large thixotropic area. The NH4-clay suspensions exhibit an intermediate behavior as there is no thixotropy, but a yield stress appears for the most concentrated suspension. These differences in macroscopic mechanical properties are discussed with reference to the suggested microscopic clay organization in suspension.

Geosynthetic clay liners (GCLs) are used in landfill liner applications and there is a need for a better control of the features of the bentonite in the GCL received on site, particularly in the European context where a wide variety of bentonites can be encountered. This paper presents the results of a project aiming at a rapid identification of the nature of the bentonite in a given GCL. The interaction between the bentonite and the fluid is increased by producing dispersions then testing its structuration in less than a few hours with filter press tests and flow curves. The results of those tests are intersected with swell index tests, electrical conductivity values and oedopermeametric tests. 2 / 29 Eight GCLs containing contrasted bentonite are studied. The two GCLs including natural calcium bentonite present poor swelling properties and high permittivities. The dispersions have low viscosity and their filtration under pressure leads to large amounts of filtrate. The two natural sodium bentonites and the four activated calcium bentonites have close permittivities, swell indices and filtrate masses. However, their rheological behaviours are different due to a difference in the values of electrical conductivity. Thus it seems that electrical conductivity measurements and rheological tests will provide a good and fast way of identifying the nature of the bentonite contained in GCLs.