Influence of Thermal Cycles on the Volume Change of Ulexite Added Sand-Bentonite Mixtures

Bentonite and sand-bentonite mixtures are recommended as engineered barriers. In waste disposal facilities, especially radioactive waste, a significant temperature increase occurs. The engineering properties of sand-bentonite mixtures change depending on temperature. Sand-bentonite mixtures used as buffer material should be able to maintain their properties unchanged at high temperatures and under thermal cycles. In the present study, the volumetric deformation behavior of sandbentonite mixtures containing 10% bentonite was investigated under room temperature and thermal cycles. In addition, ulexite, one of the boron minerals known for its high resistance to high temperature and low thermal expansion coefficient, was added to these mixtures at rates of 10 and 20% by dry weight. The compressionswelling behavior of ulexite added sand-bentonite mixtures under room temperature and thermal cycles was investigated. According to the results of the present study, when ulexite was added to the sand-bentonite mixture, the compression amount increased at room temperature, while the swelling amount decreased. However, the total compression amounts were reduced by half when thermal cycles were applied compared to the tests performed at room temperature.

Automated summary

This study investigated the volumetric deformation behavior of sand-bentonite mixtures containing 10% bentonite under room temperature and thermal cycles. Ulexite, a boron mineral known for its high temperature resistance and low thermal expansion coefficient, was added at rates of 10% and 20% by dry weight. The results showed that the addition of ulexite increased the compression amount at room temperature, while decreasing the swelling amount. However, the total compression amounts were reduced by half when thermal cycles were applied compared to room temperature tests.