混凝土二维骨料随机分布对物质扩散的影响

Influence of two-dimensional aggregate random distribution in concrete on substance diffusion

将混凝土视为骨料和砂浆组成的二相复合材料。首先建立二维骨料的随机分布模型,并改进模型骨料重叠的判断方法,在此基础上以混凝土的中性化为例,通过计算机模拟骨料随机分布对混凝土中性化时CO2扩散的延缓作用。结果表明,单个骨料的形状、大小和摆放位置都会对CO2扩散路径产生影响,而骨料集合体通过扩散路径的长度、迂曲度的变化影响扩散速度,表现为混凝土的扩散系数Da与骨料圆度α、平均粒径d和骨料含量ra具有良好的对应关系。最后,通过数值模拟确定了二维扩散中Da-α、Da-d和Da-ra的关系式,可供工程应用参考。

Concrete is regarded as a composite consisting of coarse aggregate and mortar matrix. A model of two-dimensional aggregate random distribution is developed with improving judgment of overlap between two aggregates. Based on the model, the concrete carbonization is taken as the example and the obstacle effect of aggregate random distribution in the CO2 diffusion is analyzed. The results show that the diffusion path of CO2 is influenced by the shape, size and position of the single aggregate; and aggregates influence the speed of diffusion by changing the length and the tortuosity of diffusion path. The roundness α, average diameter d and content of aggregates ra have the fine corresponding relations with the diffusion coefficient of the concrete Da. The equations are established by numerical simulation to describe the relationships Da-α, Da-d, Da-ra in two-dimensional diffusion, which are convenient for future engineering application.