基于细观复合材料的寒区混凝土导热系数模型

为分析正负温交替变化对混凝土导热系数的影响机理,进行了温变条件下混凝土导热系数模型研究。提出不同温度下的混凝土孔隙内液相(冰水相)导热系数计算理论,用以表征不同温度下混凝土内部孔隙溶液相变演化特征。从混凝土细观复合材料角度出发,将混凝土看成由等效固相、混凝土孔隙内液相(冰水相)、气相组成的三相复合材料,建立了含温度、饱和度及孔隙分布的串-并联混凝土三相复合材料导热系数计算模型,并与其它模型进行对比计算分析。研究结果表明:串-并联模型计算出的寒区混凝土导热系数与实测值有较好的一致性,且计算精度较高,相对误差范围为8.83%~24.13%;模型计算结果较好地反映了寒区混凝土导热系数与饱和度及温度间的相关关系,在温度敏感区(-10~0 ℃)内,混凝土导热系数发生骤变,变幅范围为2.59%～8.47%。混凝土孔隙内液相(冰水相)导热系数计算模型有效地刻画了温变条件下孔隙溶液相变特征,串-并联三相导热系数计算模型也客观地揭示了正负温交替变化下混凝土导热系数的演化机理。

A Thermal Conductivity Model of Concrete in Cold Region Based on Mesostructure Composite

A thermal conductivity model of concrete under temperature variation is proposed in the purpose of exploring the influence mechanism of alternating positive and negative temperatures on the thermal conductivity of concrete. The calculation theory of thermal conductivity of liquid phase (ice-water phase) in concrete pore at different temperatures is proposed to characterize the phase transformation characteristics of pore solution in concrete at different temperatures.Concrete is regarded as a three-phase composite material consisting of equivalent solid phase, liquid phase (ice-water phase), and gas phase in concrete pore. The series-parallel calculation model for the thermal conductivity of concrete as a three-phase composite material varying with temperature, saturation, and pore distribution is established and compared with other models. The thermal conductivity of concrete calculated by the present series-parallel model is in good agreement with measured values, with the relative error ranging from 8.83% to 24.13%, indicating high accuracy. The calculated results of the model well reflect the correlation between thermal conductivity and saturation and temperature of concrete in cold region. In sensitive temperature (-10 ℃~0 ℃) zone, the thermal conductivity of concrete changes abruptly with an amplitude from 2.59% to 8.47%. The liquid-phase (ice-water phase) model effectively depicts the phase transformation of pore solution under temperature variation, and the series-parallel three-phase model also objectively reveals the evolution mechanism of thermal conductivity of concrete under alternating positive and negative temperatures.