A numerical study on chloride diffusion in freeze-thaw affected concrete
A numerical study on chloride diffusion in freeze-thaw affected concrete
复制标题
冻融混凝土中氯离子扩散的数值研究
DOI：
10.1016/j.conbuildmat.2018.05.209
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发表时间：
2018-08-10
影响因子：
7.4
通讯作者：
Liu, Qing-feng
中科院分区：
文献类型：
--
作者：
Jiang, Wen-qiang;Shen, Xiao-han;Liu, Qing-feng
寒冷地区或沿海地区的混凝土在冻融循环（FTC）下会受到氯离子渗透的影响。复合劣化过程加速了混凝土的损伤演化，降低了混凝土结构的使用寿命。本文建立了一个二维、三相的细观数值模型，定量地研究了富里透水条件下氯离子的扩散机理。与现有模型不同的是，该模型通过引入一个孔隙率时间变量，考虑了混凝土冻融损伤对氯离子扩散的影响，不仅能够反映冻融作用对混凝土孔结构的影响，而且能够在时间尺度上将冻融过程与氯离子扩散过程耦合起来.第三方实验验证了该模型的可靠性。根据所获得的浓度分布曲线，分析了一系列重要的影响因素，水灰比、界面效应、外部氯离子浓度、骨料体积分数和内部温度。进一步运用灰色关联分析法对各影响因素的关联度进行排序。研究结果可为寒冷地区或沿海地区混凝土的制备技术以及在氯盐侵蚀和冻融作用下既有混凝土结构的耐久性预测提供参考。(C)2018爱思唯尔有限公司版权所有
Existing concrete in cold or coastal regions is attacked by chloride penetration under freeze-thaw cycles (FTCs). The combined deterioration process accelerate the damage evolution of concrete and reduces the service life of concrete structures. This paper presents a mesoscopic numerical model, which is 2-D and 3-phases, to investigate the mechanism of chloride diffusion under FTCs in a quantitative manner. Unlike most of existing models, the present model considers the FTCs-induced damage affected chloride diffusion by adopting a time-dependent variable of porosity, which can not only reflect how freeze-thaw action affects the concrete pore structure, but also couple the freeze-thaw process together with the chloride diffusion process at time scale. The reliability of the proposed model is validated against a third-party experiment. Based on the obtained concentration distribution profiles, a series of significant influencing factors, i.e., w/c ratio, ITZ effects, external chloride concentration, aggregate volume fraction and inner temperature are clarified. A grey relational analysis is further conducted to rank the correlative degrees of influencing factors on diffusivity of chloride under FTCs. The findings of this study can bring insights to the preparation technique of concrete in cold or coastal regions as well as the durability prediction on existing concrete structures suffering chloride attack and freeze-thaw action. (C) 2018 Elsevier Ltd. All rights reserved.