Thermal loading of smectite-rich rocks: Natural processes vs. laboratory experiments

Changes of physico-chemical properties of smectite-rich rocks (used as an engineered barrier in the nuclear waste repository) are studied. Two different genetic types of clays are evaluated—bentonite representing the residual weathering type and sedimentary montmorillonite-rich clay. Cation exchange capacity and specific surface area were determined for bulk samples (after heating experiments) and results were compared to a natural analogue (Ishirini deposit, Libya). ural changes of clay minerals were studied using XRD, TG and DTA. Two main transformation processes (illitization and kaolinization) of smectite-rich rocks followed by deterioration of physico-chemical properties were observed after heat treatment. Cation exchange capacity drops significantly with increasing temperature and so does Smicro. However, SBET values increased when heat treatment was applied.