Influence of heating and water-exposure on liquid limit of GMZ01 and MX80 bentonite

Bentonite has been considered as the buffer material for embedding canisters with high-level radioactive waste (HLW) in the deep geology repositories. GMZ bentonite deposit which is located in Xinghe County, Inner Mongolia has been proposed as buffer/backfill material for HLW repository in China. Liquid limit of natural Na-bentonite GMZ01 and commercial Na-bentonite MX80 which were previously put in the oven at 80 degrees C and 95 degrees C, and exposed to water for different times were measured. The liquid limit of GMZ01 increased slightly at the beginning, and then decreased as the heating time increased. The liquid limit of MX80 decreased as the heating time increased. The liquid limit of GMZ01 and MX80 decreased as the water-exposure time increased. After the samples were heated in the oven at 80 degrees C and 95 degrees C for several months, the mineralogical composition of GMZ01 did not exhibit evident change, the mineralogical composition of MX80 induced by thermal exhibited some change, but the chemical composition, CEC and exchangeable cation of all the samples did not show significant change. Keywords: high-level radioactive waste, deep geological disposal, bentonite, liquid limit