基于多相复合材料的混凝土导热系数预测模型

混凝土温度场分析是混凝土结构耐久性以及服役寿命预测的重要依据,而导热系数则是确定时变温度场分布的主要参数。考虑材料组成的非均质性,将混凝土视为由连续相水泥砂浆、分散相粗骨料以及二者薄弱界面过渡区(ITZ)组成的三相复合材料,并基于复合材料导热系数模型,建立了混凝土及其组成单元(水泥砂浆和ITZ界面)导热系数的计算模型;在此基础上,对比分析了水灰比、粗骨料体积分数、砂率、饱和度和界面热阻等因素对混凝土导热系数的影响规律。结果表明:混凝土导热系数随饱和度、粗骨料体积分数的增加而增大,随水灰比的增大而减小;考虑界面热阻的混凝土导热系数预测模型,能够更好地揭示饱和度与砂率对混凝土导热系数的影响机理。

Prediction model for the thermal conductivity of concrete based on its composite structure

Temperature field analysis is one of the most important criteria for predicting the durability and service life of concrete structures, and thermal conductivity is commonly regarded as an important parame-ter to determine the time-dependent temperature field. With consideration of the non-homogeneous character-istic of the material composition, a mesoscale approach, in which concrete is described as a three-phase composite consisting of the coarse aggregate, hardened cement mortar matrix and the interfacial transition zone (ITZ) between them, is adopted to develop the thermal conductivity of the mortar and ITZ compo-nents with in concrete in terms of the composite model. Compared with the experimental results existed in the literature, effect of various factors, such as the water-cement ratio, volume fraction of aggregate, sand ratio, saturation degree and the interfacial thermal resistance, on the thermal conductivity was discussed. The results show that thermal conductivity of concrete increases with an increase of saturation and aggre-gate volume fraction, but decreases with the increase of water-cement ratio. The influence of water satura-tion degree on thermal conductivity is well presented by means of the proposed model taking into account the interfacial thermal resistance.