Effects of synthetic site water on bentonite-concrete system for a potential nuclear waste repository  

作　　者：Zhao Sun Yong-Gui Chen Wei-Min Ye Qiong Wang Dong-Bei Wu Zhen-Yu Yin 

机构地区：[1]Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education,Department of Geotechnical Engineering,Tongji University,Shanghai,200092,China [2]Department of Civil and Environmental Engineering,The Hong Kong Polytechnic University,Hung Hom,Kowloon,Hong Kong,China [3]School of Chemical Science and Engineering,Tongji University,Shanghai,200092,China

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2024年第9期3786-3797,共12页岩石力学与岩土工程学报（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.42125701);the Innovation Program of Shanghai Municipal Education Commission(Grant No.2023ZKZD26);Fund of the Shanghai Science and Technology Commission(Grant No.22DZ2201200);Top Discipline Plan of Shanghai Universities-Class I and the Fundamental Research Funds for the Central Universities;Financial support from the International Post-Doc Fund of The Hong Kong Polytechnic University is greatly appreciated.

摘　　要：In high-level nuclear waste(HLW)repositories,concrete and compacted bentonite are designed to be employed as buffer materials,which may raise a problem of interactions between concrete and bentonite.These interactions would lead to mineralogy transformation and buffer performance decay of bentonite under the near field environment conditions in a repository.A small-scale experimental setup was established to simulate the concrete-bentonite-site water interaction system from a potential nuclear waste repository in China.Three types of mortars were prepared to correspond to the concrete at different degradation states.The results permit the determination of the following:(1)The macroproperties of Gaomiaozi(GMZ)bentonite(e.g.swelling pressure,permeability,the final dry density,and water content of reacted samples);(2)The composition evolution of fluids from the synthetic site water-concrete-bentonite interaction systems;(3)The sample characterization including Fourier transform infrared spectroscopy(FTIR)and X-ray powder diffraction(XRD).Under the infiltration of the synthesis Beishan site water(BSW),the swelling pressure of bentonite decreases slowly with time after reaching its second swelling peak.The flux decreases with time during the infiltrations,and it tends to be stable after more than 120 d.Due to the cation exchange reactions in the BSW-concrete-bentonite systems,the divalent cations(Ca and Mg)were consumed,and the monovalent cations(Na and K)were released.The dissolution of minerals in the bentonite such as albite causes Si increasing in the pore water.It was concluded that the hydro-mechanical property degradation of bentonite takes place when it comes into contact with concrete mortar,even under low-pH groundwater conditions.The soil dispersion,the uneven water content,and the uneven dry density in bentonite samples may partly contribute to the swelling decay of bentonite.Therefore,the direct contact with concrete has an obvious effect on the performance of bentonite.

关 键 词：Mock-up device GMZ bentonite Site water-concrete-bentonite system Geochemistry Buffer performance 

分 类 号：TU443[建筑科学—岩土工程]