Simulation of Chloride Diffusivity for Cracked Concrete Based on RBSM and Truss Network Model
Simulation of Chloride Diffusivity for Cracked Concrete Based on RBSM and Truss Network Model
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DOI：
10.3151/jact.6.143
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发表时间：
2008
影响因子：
2
通讯作者：
Licheng Wang;Mitsutaka Soda;T. Ueda
中科院分区：
文献类型：
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作者：
Licheng Wang;Mitsutaka Soda;T. Ueda
对于盐环境下的混凝土结构，混凝土的微观结构和裂缝对氯离子的侵入起着至关重要的作用。在这项研究中，混凝土被模拟在细观尺度上作为一个三相复合材料，即，骨料颗粒、砂浆和界面过渡区（ITZ）。由于刚体弹簧模型在预测混凝土裂缝行为方面的优势，本文采用刚体弹簧模型对混凝土进行力学分析，以模拟混凝土微裂缝的分布和宽度。在此基础上，采用桁架网络模型计算了开裂混凝土的氯离子扩散系数。通过对混凝土和砂浆扩散系数的统计分析，从理论上阐明了界面扩散系数的含义。根据不同的假设厚度，本文估算的界面扩散系数范围约为砂浆扩散系数的3-16倍，与前人的实验结果吻合较好。为了验证微裂纹对混凝土扩散性能的影响，对不同应力水平下的混凝土试件进行了氯离子渗透数值分析。分别研究了轴压和轴拉荷载作用下开裂混凝土的氯离子扩散系数随应力水平的变化规律。结果表明，氯离子扩散系数是显着依赖于应力水平，但只考虑裂纹的影响RBSM预测是不够的。因此，提出了一个能反映混凝土在荷载作用下微观结构变化的经验公式。利用该模型，可以合理地估算开裂混凝土的氯离子扩散系数。
For concrete structures exposed to salt environment, the microstructure and cracks play a crucial role in the ingress of chloride ions into concrete. In this study, concrete is simulated on the meso scale as a three-phase composite, i.e., aggregate particles, mortar and the interfacial transition zone (ITZ). Because of the advantages in predicting cracks behavior in concrete, Rigid Body Spring Model (RBSM) is employed to carry out the mechanical analysis to simulate the distribution and width of microcracks. And then, the truss network model is adopted to evaluate the chloride diffusivity of the cracked concrete. On the basis of the statistics analysis of diffusion coefficients of concrete and mortar determined experimentally, the diffusivity of ITZ is analytically clarified. The range of diffusion coefficient of ITZ estimated in this paper is approximately 3-16 times of that of mortar depending on the different assumed thickness, which agrees well with that of the previous experimental results. With the aim to validate the effect of microcracks on the diffusivity of concrete, a series of the chloride ions penetrating analysis is numerically carried out on the concrete specimen under different stress levels. The axial compressive and tensile loading conditions are investigated respectively and the effects of stress level on chloride diffusivity of cracked concrete are examined. Results indicate that the chloride diffusivity is significantly dependent on the stress level, but only considering the effect of cracks predicted by RBSM is not sufficient. So an empirical equation which can account for the microstructure variation of concrete under loading is proposed. With it, a reasonable estimation for chloride diffusivity of cracked concrete is achieved.