混凝土中氯离子扩散分析的两相边界元模型

摘要

A two-phase model of boundary element method( BEM)is proposed to study the diffusion behavior of chloride in concrete. The concrete is treated as a two-phase heterogeneous material composed of mortar and coarse aggregate. The chloride diffusion is as-sumed to take place only in the mortar. The diffusion problem of chloride in concrete with aggregate is solved by BEM with a multiply connected domain. By modeling concretes with different coarse aggregate′s content,particle size and arrangement,the effect of coarse aggregate on the chloride diffusion is examined. Contrasted with the finite element model,the two-phase BEM model is proved to be reasonable and of more advantage,indicating that the proposed model can be used to analyze the chloride diffusion in concrete. The re-sults show that coarse aggregate obstructs the diffusion of chloride in concrete,and the content of coarse aggregate has a significant im-pact on decreasing the capability of diffusion and changing the concentration distribution of chloride in field.%提出了一个两相混凝土的多连域边界元模型，用来研究混凝土中的氯离子扩散与分布规律。将混凝土看作由砂浆和粗骨料组成的两相非均匀材料，并假定氯离子扩散只发生在砂浆浆体中。建立了混凝土中氯离子扩散的多连域边界元模型，分析了粗骨料粒径、含量和排列方式对混凝土中氯离子扩散和分布规律的影响。通过与有限元模型的对比证明了提出的两相多连域边界元模型的合理性和优势，说明本研究模型可以用于混凝土中氯离子扩散的分析。研究结果表明，粗骨料的存在会形成阻滞作用，引发氯离子浓度场的局部梯度变化；粗骨料的含量对混凝土中氯离子扩散的阻滞作用影响明显。