Experimental investigation and numerical simulation for chloride diffusivity of cement paste with elliptical cement particles
Experimental investigation and numerical simulation for chloride diffusivity of cement paste with elliptical cement particles
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DOI：
10.1016/j.conbuildmat.2022.127616
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发表时间：
2022-04-27
影响因子：
7.4
通讯作者：
Zheng, Jian-jun
中科院分区：
文献类型：
--
作者：
Zhang, Jian;Wang, Hai-long;Zheng, Jian-jun
水泥颗粒的形状通过其比表面积和分散形态影响水泥的水化过程，进而对水泥浆体的孔结构特征和氯离子的侵入产生重大影响，而在大多数水泥水化矢量模型中，水泥颗粒的形状一般被简化为球形。为了揭示水泥颗粒形状对氯离子扩散系数的影响，提出了一种定量分析水泥颗粒形状对氯离子扩散系数影响的数值方法。根据水泥颗粒的尺寸分布曲线和周期性分布，首次构建了具有代表性的新拌水泥浆体中的椭圆夹杂。根据水化层厚度在准椭圆表面附近均匀增加的规律和水化层重叠引起的干涉效应，建立了基于矢量的水泥水化模型，并讨论了水泥颗粒长径比对水化程度的影响。考虑多相复合水泥浆体的扩散特性，提出了适合二维像素模型的首次通过理论，并应用了相应的布朗运动算法。利用高倍显微镜，计算水泥颗粒的平均长径比。通过对8组实验结果的充分比较，验证了该估计方法的有效性。最后得出了椭圆水泥颗粒长径比对氯离子扩散系数的影响。
The shape of cement particle affects the hydration process of cement through its specific surface area and dispersion morphology, and then exerts great effects on the pore structure characteristic and the chloride ingression of cement paste, while it is generally simplified as the sphere in most of the vector models of cement hydration. To reveal the influence of cement particle shape on chloride diffusivity, a numerical method for quantitative analysis was proposed in this work. According to the size distribution curve and periodic distributions of cement particles, a representative fresh cement paste with elliptical inclusions was firstly constructed. According to the regulations of uniform increase of the thickness of hydration layer around the surface of quasi ellipse and the interference effects induced by hydration layer overlapping, a vector-based model of cement hydration was established and the influence of aspect ratio of cement particles on the hydration degree was discussed. By considering the diffusion properties of the multi-phase composite cement paste, the first-passage theory suited to two-dimensional pixel model was proposed, and the corresponding Brownian motion algorithm was applied. Using high power microscope, the average aspect ratio of cement particles was calculated. By full comparison of eight groups of experimental results, the effectiveness of this estimation method was verified. At last, the influence of the aspect ratio of elliptical cement particles on chloride diffusivity was drawn.