Increasingly stringent regulation of pollution and waste production worldwide drives the need to isolate contaminants that pose a threat to human and environmental health by using engineered barrier systems. The relatively low cost and wide versatility of reactive barriers favour the use of bentonite as an important component in barrier systems. Current research aims to optimise the performance of bentonite-based barriers under the effects of coupled thermal, mechanical, hydraulic and chemical stresses, for a wide range of pollutants and over long time periods - tens of thousands of years in the case of nuclear waste.