Akademik Veri Yönetim Sistemi
PAMUKKALE UNIVERSITY JOURNAL OF ENGINEERING SCIENCES-PAMUKKALE UNIVERSITESI MUHENDISLIK BILIMLERI DERGISI, cilt.31, sa.5, ss.841-848, 2025 (ESCI, TRDizin)
Compacted bentonite as a buffer and/or backfill material in deep geological repositories is recommended to safely dispose of high-level nuclear waste. The high swelling potential and low permeability properties of bentonite are the main bases for this recommendation. Bentonite used in the repositories will hydrate with groundwater to form a self-sealing barrier while exposed to the high temperature emitted from the canister. In this process, the outer zones tend to swell, while the zones close to the canister may become unsaturated due to the high temperature. These conditions can affect the hydraulic and mechanical properties of bentonite and limit its long-term performance. Therefore, determining soil-water characteristic curves and swelling pressure at different thermal conditions is of great importance for evaluating groundwater movement and sealing properties of bentonite. Temperature cycles can adversely affect critical properties of bentonite, such as water retention capacity and swelling pressure. In this study, Etibor-48 (E-48) boron mineral, known for its low thermal expansion properties, was used as an additive to improve the engineering properties of bentonite under high temperature conditions. E-48 mineral was added to the compacted bentonite at 10% and 20% ratios, and the swelling pressure and soil-water characteristic curves of the mixtures were investigated at room temperature and high temperature (80 degrees C) conditions. The swelling pressure tests were performed using the constant volume method in an oedometer system, and the soil-water characteristic curves were determined using the vapor equilibrium technique. The results showed that high temperature and E-48 addition decreased the water retention capacity and swelling pressure of bentonite. It was also found that the drying path did not overlap with the wetting path, and the additive-free bentonite had a higher water retention capacity than the E-48-added mixtures. These results provide important insights into understanding the effect of additives to evaluate and optimize the performance of bentonite-based buffer materials under high-temperature conditions.