摘要
应用膨胀剂补偿水泥基材料干燥收缩时,其补偿效果的发挥与化学结合水和物理吸附水的演化密切相关,多数细微观测试分析手段都要求对试件进行干燥预处理,难以辅助分析补偿收缩的时间发展历程。利用原位无损的低场磁共振弛豫技术,结合宏观质量和长度测试,对持续水养和高湿度空养的掺膨胀剂净浆进行长期监测,从水分状态和含量角度,定量分析化学结合水与物理吸附水的演化规律,进而解析净浆的补偿收缩变形。结果表明:在持续水养过程中,从水养第3 d起算,净浆质量、膨胀变形、可蒸发水含量均持续增大,但增加速率逐渐降低。掺硫铝酸钙类或氧化镁类膨胀剂可明显增大净浆化学结合水增量及其单位增量导致的膨胀变形,但几乎不影响物理吸附水的演变规律及其单位增量导致的膨胀变形。在高湿度(98%相对湿度)空养过程中,从空养第0d(水养第56d)起算,净浆质量先降低、后升高;净浆先收缩、后膨胀;可蒸发水含量在前28 d内迅速降低,后保持稳定。掺硫铝酸钙类或氧化镁类膨胀剂会增大净浆前期可蒸发水含量降幅,也会增大后期膨胀变形以补偿收缩。掺膨胀剂水泥基材料的膨胀过程极其复杂,利用低场磁共振技术并结合其它测试方法实现膨胀变形的精确解析,有助于完善膨胀机理,并协助选用膨胀剂。
Introduction The volumetric deformation of cement-based materials continues over setting,hardening and service periods,as a result of both cement hydration and changes in temperature and humidity.Under restricted conditions,excessive volume shrinkage may lead to cracking in cement-based materials,seriously threatening the long-term performance and durability of structure.As an important admixture to compensate for shrinkage and to control cracking,expansive agents are widely used in engineering construction.The influence of expansive agents on the compensatory effect for drying shrinkage of cement-based materials is closely linked to the evolution of chemically bound water and physically adsorbed water.Since most mesoscopic and microcosmic testing techniques require drying preparations for specimens,it is challenging to analyze the development process of shrinkage-compensating.Low-field nuclear magnetic resonance (LF-NMR) technique has a unique technological advantage for investigating cement-based materials.Taking hydrogen nuclei in water as a probe,LF-NMR technique can non-destructively,rapidly and accurately characterize the pore water content and water distribution in specimens in situ,which promotes to accurately analyze the connection between micro change of pore water and macro volumetric deformation.Therefore the cement paste samples mixed with expansive agents are monitored by non-destructive LF-NMR technique in this work,the weight and length are also measured.From the perspective of water content and its state,the quantitative analysis on evolution of chemically bound water and physically adsorbed water is conducted.Furthermore,the shrinkage-compensating deformation of cement paste is thoroughly analyzed.Methods White cement,calcium sulfoaluminate and MgO expansive agents (CSA and MEA) are used to prepare cement paste specimens.Water to cement ratio (W/C) is 0.40,and the weight ratio of expansive agent to cement is 5%.The expansion agents are produced by Wuhan Sanyuan Special Building Materials Co.The
作者
梁华明
张笑与
郭鑫志
周春圣
LIANG Huaming;ZHANG Xiaoyu;GUO Xinzhi;ZHOU Chunsheng(School of Civil Engineering,Harbin Institute of Technology,Harbin 150090,China)
出处
《硅酸盐学报》
EI
CAS
CSCD
北大核心
2024年第11期3546-3553,共8页
Journal of The Chinese Ceramic Society
基金
中国高校基本科研业务费专项(HIT.OCEF.2021022)。
关键词
膨胀剂
化学结合水
物理吸附水
低场磁共振技术
expansive agent
chemically bound water
physically adsorbed water
low-field nuclear magnetic resonance technique
