聚丙烯酸钠改性钙基膨润土工程特性及微观结构研究  

Engineering properties and microstructure of sodium polyacrylate-modified calcium bentonite

作　　者：陈宏信 牛松荧 冯世进[1,3] 薛钦培 李正霏 石福江 CHEN Hongxin;NIU Songying;FENG Shijin;XUE Qinpei;LI Zhengfei;SHI Fujiang(Department of Geotechnical Engineering,Tongji University,Shanghai 200092,China;Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education,Shanghai 200092,China;State Key Laboratory of Disaster Reduction in Civil Engineering,Shanghai 200092,China)

机构地区：[1]同济大学地下建筑与工程系,上海200092 [2]同济大学岩土及地下工程教育部重点实验室,上海200092 [3]土木工程防灾减灾全国重点实验室,上海200092

出　　处：《岩土工程学报》2025年第4期860-868,共9页Chinese Journal of Geotechnical Engineering

基　　金：国家重点研发计划项目(2023YFC3707904);国家自然科学基金项目(42077250,42277148)。

摘　　要：中国钙基膨润土(CaB)资源丰富,近年来作为竖向隔离墙膨润土泥浆的替代材料备受关注。然而,由于天然钙基膨润土膨胀能力与化学相容性较差,对其工程特性的改进成为关键问题。为此,研究以聚丙烯酸钠(PAAS)为改性剂对钙基膨润土进行改良,确定了制浆—干燥—研磨法制备聚丙烯酸钠改性钙基膨润土(PAAS―CaB)的最佳制备条件。系统测试了改性膨润土的工程特性及微观结构,结果表明,改性剂掺量为8%时,PAAS―CaB膨胀指数可达34.0 mL/(2g),聚丙烯酸钠改性显著提高了钙基膨润土的吸水膨胀性能及化学相容性,为降低了膨润土泥饼的渗透系数。随PAAS掺量的增加,泥浆马氏黏度增大,滤失量和pH值减小,泥浆密度则主要由膨润土掺量控制。与未改性的CaB相比,PAAS―CaB在微观上表现出整体性更好的片层结构、更小的蒙脱石晶层间距。聚丙烯酸钠主要通过桥联包覆作用与接枝共聚合作用改善钙基膨润土性能。研究为优化PAAS―CaB制备工艺提供了可靠依据,为CaB的工程应用提供了可行的技术路径。The abundant calcium-based bentonite(CaB)resources in China have gained attention as potential alternatives for preparing slurry when constructing cut-off walls.However,the limited swelling capacity and chemical compatibility of natural CaB pose critical challenges to enhancing its engineering properties.In this study,sodium polyacrylate(PAAS)is employed as a modifier to ameliorate CaB,and the optimal preparation conditions for sodium polyacrylate-modified calcium-based bentonite(PAAS―CaB)are determined through the processes of slaking,drying and grinding.The systematic tests on the engineering properties and microstructure of the modified bentonite were conducted.The results reveal that at a modifier content of 8%,the swelling index of PAAS―CaB reaches 34.0 mL/2g.The sodium polyacrylate modification significantly enhances the water absorption and swelling performance of CaB,along with improving its chemical compatibility,resulting in reduced permeability coefficient of the bentonite cake.With the increasing PAAS content,the Marsh viscosity of slurry increases,while the filtration loss and pH value decrease.The slurry density is primarily controlled by the bentonite content.Compared to the unmodified CaB,PAAS―CaB exhibits a superior overall lamellar structure at a microscopic scale,characterized by a smaller interlayer distance of montmorillonite crystalline layers.The sodium polyacrylate primarily modifies the calcium-based bentonite through bridging encapsulation and graft copolymerization.This study establishes a reliable foundation for optimizing the preparation process of PAAS―CaB and presents a feasible technical pathway for the engineering application of the calcium-based bentonite.

关 键 词：隔离墙 钙基膨润土 聚丙烯酸钠 工程特性 微观结构 

分 类 号：TU411[建筑科学—岩土工程]