ESEM study of osmotic swelling of bentonite from Radzionkow (Poland)

Swelling tests using an environmental scanning electron microscope (ESEM) have been carried out on bentonite of Carboniferous age from the Radzionkow coal mine, Poland. The bentonite consists mostly of smectite in which sodium is the main exchangeable cation. ESEM test results revealed that in all samples osmotic swelling of constituent smectite in response to freshwater immersion led to significant microstructural reorganisation, similar to that recently recorded for freshwater-treated, smectitic clay in reservoir sandstones. Freshwater exposure caused the bentonite to become significantly less compact and more (micro)porous due to osmotic swelling of constituent smectite.