多边形骨料混凝土氯离子扩散系数预测

提出了多边形骨料混凝土氯离子扩散系数计算的数值方法。通过各向均匀放缩和单向均匀放缩，生成符合给定级配、长细比和含量的多边形骨料，将生成的骨料投放到具有周期性边界条件的模拟试件中重构混凝土细观结构。再将混凝土细观结构规则离散，应用像素点计数法通过分析骨料和界面含量的收敛性确定所需的像素点个数。应用Fick第一定律，在傅里叶空间中导出了非均匀介质中氯离子浓度梯度解。基于这个解，提出了混凝土氯离子扩散系数计算的迭代算法。与有限元法相比，该数值方法具有无需复杂的网格剖分、数据储存量少、计算简单的优点。最后，与两组试验结果比较，验证了该数值方法的有效性，并讨论了骨料长细比对混凝土氯离子扩散系数的影响。

Prediction of chloride diffusivity of concrete with polygonal aggregates

A numerical method is presented for calculating the chloride diffusivity of concrete with polygonal aggregates. Through uniform scaling and unidirectional scaling, we generate polygonal aggregates for a given gradation, aspect ratio and content, and reconstruct the mesostructure of concrete by placing the generated particles into a simulation element with periodic boundary conditions. The mesostructure of concrete is then discretized on a regular grid, and a pixel-counting method is used to analyze the convergence of aggregate content and interfacial transition zone content to determine the required number of pixels. By applying Fick’s first law, we derive a solution for the chloride concentration gradient in heterogeneous media in the Fourier space, and based on this solution, develop an iterative algorithm for calculating the chloride diffusivity of concrete. Compared with the finite element method, our numerical method has the advantages of no need for complicated mesh generation, smaller data storage, and easy calculation. Finally, the method is verified through comparison with two sets of experimental data, and the effect of aggregate aspect ratio on the chloride diffusivity of concrete is discussed.