基于细观复合材料的混凝土导热系数模型

混凝土温度场分析是混凝土结构耐久性劣化、温度应力、火灾作用下结构破坏以及建筑节能分析的关键内容,而导热系数是确定温度场的重要参数。在细观尺度上,将混凝土看作由连续相水泥砂浆和分散相粗骨料组成的两相复合材料。分析了两相复合材料等效导热系数理论模型,将其用于混凝土等效导热系数的预测并与实测值进行比较,发现饱和混凝土即使采用不考虑界面热阻模型仍与实测结果吻合较好,而干燥混凝土必须考虑界面热阻的影响。为提高混凝土导热系数理论模型的预测精度,还应考虑粗骨料形状、级配、水泥砂浆与粗骨料间界面热阻以及孔隙率、含水率等方面的影响。

Theoretical Models of Effective Thermal Conductivity of Concrete Based on Composite Materials in Mesoscale

Temperature field analysis is one of the key contents for the analysis of durability,temperature stress,damage of structures under fire and energy efficiency in concrete structures,and thermal conductivity is an important parameter to determine the time-dependent temperature field.Considering that the concrete can be treated as a kind of two-phase composite materials composed of cement mortar and coarse aggregate in the mesoscale,theoretical models for effective thermal conductivity of two-phase materials were compared and analyzed.The calculated thermal conductivities of concrete materials by using these models were compared with the experimental results.It was found that the results calculated by using the models ignoring interfacial thermal resistance are in good agreement with the experimental results of saturated concrete materials while the impact of interfacial thermal resistance must be considered for dry concrete materials.To improve the accuracy of theoretical models for thermal conductivity of concrete materials,the influence of shape and grading of coarse aggregates,interfacial thermal resistance between cement mortar and coarse aggregates,porosity,moisture content should be taken into account.