The analysis of thermal conduction and thermal stress of concrete at mesoscopic level indicates that the heterogeneity of concrete plays an important role on its thermal and mechanical behavior. The results show that the influence of heterogeneity on the mechanical behavior of concrete is greater than that of thermal behavior. However, the coarse aggregates significantly influence both the thermal and mechanical behavior of concrete. The thermal stress caused by the mismatch of temperature gradient and thermal expansion may easily result in thermal cracking of concrete. The cracking process induced by temperature gradient is closely related to the thermal conductivity of concrete. The simulation of crack initiation and propagation processes of thick-walled concrete sample heated in an inner hole shows that the crack evolution can be divided into four stages, which agrees well with the experimental results. The cracking process modeling shows that the localization effect of crack propagation is the essential cause of major crack formation.%通过对混凝土热传导与热应力细观特性的分析，探讨细观非均匀性对混凝土热学和力学性能的影响作用。计算结果表明：细观非均匀特性对混凝土导热性能的影响并不明显，但对其力学性能的影响作用却不能忽视；骨料颗粒对混凝土的热学和力学性能都有显著的影响作用。温度梯度和热膨胀不匹配共同作用所产生的温度应力极容易导致混凝土开裂，其中温度梯度引起的混凝土开裂过程与热传导系数密切相关。通过对厚壁筒混凝土试样在孔内温度升高情况下裂纹萌生和扩展过程的数值模拟研究，从机理上揭示试验观测的四个裂纹发展阶段。研究结果表明裂缝扩展的局部化效应是主裂纹形成的根本原因。
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