水泥基复合材料氯离子扩散系数与孔隙率之间的关系

Relationship between porosity and chloride diffusivity in cement-based composite materials

为了研究水泥基复合材料中孔隙率对氯离子扩散系数的影响,成型了不同水灰比,含骨料体积分数、粒径与级配不同的砂浆试样;采用稳态电加速法测试氯离子扩散系数、压汞技术测试孔结构参数、微焦点计算机断层扫描技术(X-CT)可视化孔结构分布,系统地研究了水泥基复合材料氯离子扩散系数与其骨料体积分数、总孔隙率、毛细孔隙率、连通孔径之间的关系。结果表明:骨料与基体之间的界面过渡区(界面区)显著地改变了水泥石中孔结构分布,水灰比越小,多孔的界面区对材料孔隙率的影响越显著;水泥基复合材料的氯离子扩散系数与其总孔隙、毛细孔隙率之间有很好的相关性,与其连通孔径几乎成线性关系,连通孔径越大,氯离子的扩散系数越大。

For investigating the effect of porosity in cement-based composite materials on diffusion coefficient of chloride ion,a series of mortar specimens with different water-cement ratios,different volume fractions and different diameters and graduation of aggregates are cast,and then chloride diffusivity of mortar specimens are measured by steady-state electric acceleration method and pore structure parameters of corresponding samples are obtained by mercury intrusion porosimetry.At the same time,the pore size distributions are visualized by X-ray micro-focus computer tomography.The results show that porous interfacial transition zones between aggregate and bulk cement paste significantly change the distribution of pore structure in hardened cement paste,and the smaller water-cement ratio is,the more significant the effect of interfacial transition zones on pore structures of hardened cement paste is.A good correlation between the total porosity,capillary porosity and the diffusion coefficient of chloride ion in cement-based composite materials has been determined and the continuous pore diameter is linearly related to the diffusion coefficient of those.Furthermore,the larger the continuous pore diameter is,the larger the value of chloride diffusivity is.