高温强碱条件下膨润土物理性能的时效性  

Aging effect on physical properties of bentonite under high temperature-strong alkaline conditions

作　　者：曾召田[1] 张瀚彬 吕海波[1,2] 车东泽 潘斌 ZENG Zhaotian;ZHANG Hanbin;LV Haibo;CHE Dongze;PAN Bin(Guangxi Key Laboratory of Geomechanics and Engineering,Guilin University of Technology,Guilin 541004,Guangxi,P.R.China;School of Architecture and Electrical Engineering,Hezhou University,Hezhou 542899,Guangxi,P.R.China)

机构地区：[1]桂林理工大学广西岩土力学与工程重点实验室,广西桂林541004 [2]贺州学院建筑与电气工程学院,广西贺州542899

出　　处：《土木与环境工程学报(中英文)》2025年第2期49-56,共8页Journal of Civil and Environmental Engineering

基　　金：国家自然科学基金(41962014、42167020);广西自然科学基金(2018GXNSFDA281038、2019GXNSFAA245025)。

摘　　要：在深地质处置库运营过程中,作为缓冲层材料的膨润土将长期处于高温强碱环境中,其物理性能会随时间发生劣化效应。为探讨高温强碱条件下膨润土物理性能的时效性,对MX-80膨润土粉末进行不同时长(t=0、15、30、45、60、90 d)的高温强碱作用预处理(温度T=90℃,碱溶液浓度CNaOH=0.5 mol/L),通过室内试验研究了MX-80膨润土的比重、比表面积和膨胀指数等物理性能指标随反应时长t的变化规律,并选择部分代表性试样进行X射线衍射(XRD)试验和热重分析(TGA)试验,从微观角度对高温强碱条件下膨润土物理性能的时效性进行解释。结果表明,高温强碱作用预处理后,MX-80膨润土的比重、比表面积和膨胀指数在0~45 d内急剧下降,45 d后趋于稳定,90 d后三者降幅分别为13.6%、18.5%、58.1%;膨润土的主要矿物蒙脱石含量大幅减少,钠长石含量有所增加,90 d后二者变化量分别为-23.3%、+3.7%;膨润土颗粒吸附的自由水、弱结合水和强结合水的含量减少,90 d后三者含量分别减少2.84%、0.13%、0.24%;高温强碱条件下膨润土物理性能随时间发生劣化效应的根本原因在于膨润土中有效成分蒙脱石发生溶解,其含量下降导致比重、膨胀指数和比表面积降低。During the operation of deep geological repository,the bentonite as a buffer material would be in a high temperature-strong alkaline environment for a long time,and its physical properties would deteriorate with time.Aging effect on physical property of MX-80 bentonite powder at high temperature and strong alkali conditions was investigated in this paper.MX-80 bentonite was subjected to alkali-heat conditions,i.e.,T=90℃and CNaOH=0.5 mol/L for duration of 0,15,30,45,60,90 days,respectively.The variation of physical properties such as the specific gravity,specific surface area and swell index of MX-80 bentonite was studied through laboratory experiments.Some representative specimens were selected for X-ray diffraction(XRD)tests and thermogravimetric analysis(TGA)tests to provide a reasonable explanation from microscopic perspective.The results showed that the specific gravity,specific surface area and swell index of bentonite decreased sharply from 0 to 45 days,gradually levelling off after then,finally,the reduction amplitudes were 13.6%,18.5%and 58.1%after 90 days,respectively.Montmorillonite content decreased and albite content increased.The changes of montmorillonite and albite were-23.3%and+3.7%after 90 days.The content of free water,weakly bound water and strongly bound water decreased,and the content of the three decreased by 2.84%,0.13%and 0.24%respectively after 90 days.The fundamental reason for the deterioration of bentonite physical properties over time under high temperature and strong alkali conditions was the dissolution of montmorillonite.

关 键 词：膨润土 高温强碱条件 物理性能 时效性 蒙脱石溶解 

分 类 号：TU443[建筑科学—岩土工程]