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Laboratory performance of two bentonites used in a Brazilian geosynthetic clay liner

This paper presents the results of several laboratory tests carried out in two samples of bentonite clay, provided by the same supplier, largely used in the Geosynthetic Clay Liner (GCL) Brazilian industry for sanitary landfill liner applications. The difference between the samples was that one of them was grainy (Sample A) and the other was in powder (Sample B). The tests were natural humidity, grain size distribution, specific weight, Atterberg limits, swelling index, free expansion, swelling pressure, consolidation properties and coefficient of permeability. The presence of clay on the samples was similar: 74% for sample A and 78% for sample B, and their unit weight of solids resulted in 2.87 g/cm3 (sample A) and 2.79 g/cm3 (sample B). The results showed that sample B had slightly better properties than sample A when used as a liner. Its colloidal activity, which is indicative of the expansive potential of the bentonite, was 3.7 (bigger than the result of sample A, which was 3.6). The swelling test results pointed to the same direction: only the powder sample (B) reached the reference standard (≥24 mL/2g). As expected, the permeability coefficients, determined for different applied loads, reduced when the applied load was increased.