水泥基复合材料湿度扩散特性细观数值模拟研究

运用Weibull统计分布方法描述材料的非均匀性,并结合质量扩散与统计分布理论建立了水泥基复合材料湿度扩散的细观数值模型.对水泥基复合材料内湿度变化规律的数值模拟研究表明：砂浆的湿度场不仅受温度的影响,还受到湿度本身的影响,湿度和温度的升高对湿度的扩散具有加速作用.砂浆的细观非均匀性对湿度扩散影响显著.试样的均匀程度越低,其内包含的孔隙就越多,这有利于湿度的扩散;反之,如果试样的均匀程度越高,则越不利于湿度的扩散.砂浆试样的宏观有效湿度扩散系数随Weibull分布函数中均质度系数的增加呈负指数衰减趋势.在混凝土中,骨料颗粒占有较高的体积分数,而其湿度扩散性能却较低,这在一定程度上降低了混凝土的宏观湿度扩散性能.研究结果表明,混凝土的湿度扩散系数随其骨料含量增加基本呈线性递减变化关系.

Numerical simulation research on humidity diffusion characteristics of cement-based composites at mesoscopic level

On the basis of mass diffusion and statistical distribution theories,a numerical model is established to simulate the humidity diffusion processes of cement-based composites at mesoscopic level.Weibull distribution method is used to describe the heterogeneity feature of materials in the numerical model.The numerical study of humidity diffusion in cement-based composites shows that: temperature and humidity conditions significantly affect the humidity fields of mortar matrix,the increasing of humidity and temperature can accelerate the humidity diffusion.The heterogeneity feature of mortar matrix significantly influences its humidity diffusion.Strong heterogeneity of mortar matrix indicates that it contains more pores,which is beneficial to the humidity diffusion,otherwise,strong homogeneity of material is not good for humidity diffusion.The effective humidity diffusion coefficient of mortar matrix decreases as a negative exponential mode with the increasing of heterogeneity index in Weibull distribution function.For the concrete,low humidity diffusion coefficient of aggregates and high volume fraction of aggregates significantly reduce the effective humidity diffusion coefficient of concrete.The results indicate that the effective humidity diffusion coefficient of concrete decreases linearly with the increase of volume fraction of aggregate.