ABSTRACT
Bentonite-sand mixtures are commonly used as buffer/backfill materials for isolating high-level wastes in geological repositories. In recent years, graphite is gaining significant attention as an additive in bentonite mixtures due to its high thermal conductivity. Buffer/backfill materials should have sufficient strength to securely support and maintain position of canisters. Unconfined compressive strength (UCS) is an important factor in understanding mechanical performances of barrier materials. Therefore, this study investigated UCS of compacted bentonite-sand (BS) and bentonite-graphite-polypropylene fiber (BGF) mixtures at different temperatures under constant moisture condition. Test results showed that UCS of both BS and BGS mixtures increased with water content and temperature. Additionally, the change in UCS with temperature was more pronounced in BS mixtures. However, comparing both BGF and BS mixtures at 27℃, BGF mixture exhibits higher UCS, believed due to higher tensile resistance of fiber, altering uniaxial stress state to triaxial stress state and increases compressive strength.
