干燥条件下水泥基材料中氧气扩散预测模型

Prediction Model of Oxygen Diffusion in Cement-based Materials under Dry Condition

将氧气在水泥基材料中的扩散分为Knudsen型扩散、过渡型扩散及Fick型扩散3类,并将水泥基材料孔结构简化为平行管束模型。根据孔尺寸分布密度函数,将3种扩散方式进行定量化表征,结合孔隙率和孔曲折度,建立了干燥条件下水泥基材料的氧气扩散系数预测模型。利用自主研制的氧气扩散系数测定装置对干燥条件下砂浆试件的氧气扩散系数进行测定,结果表明试验值与预测模型计算值吻合度较好,且3种扩散方式中以过渡型扩散和Fick型扩散为主。

The diffusion of oxygen in cement-based materials is divided into three parts, i.e., the Knudsen diffusion, the transitional diffusion and the Fick diffusion. The pore structure of cement-based materials is simplified as a parallel tube bundle. The three diffusion modes are characterized quantitively based on the density function of pore size distribution. Combined with the porosity and the tortuosity, the oxygen diffusion prediction model of cementitious materials under dry conditions was proposed. The oxygen diffusion coefficients of mortars were measured by an invented oxygen diffusion coefficient measuring device to verify the simulated data by the theoretical model. The experiment results are in reasonable agreement with the simulated data. Moreover, the transitional diffusion and the Fick diffusion are the main modes among the three diffusion modes.