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中文摘要：
混凝土的扩散渗透性能与其微观结构（包括细观尺度上粗骨料颗粒与砂浆之间的界面过渡区及砂浆本身的微观结构等）密切相关。在微观尺度上,砂浆和界面过渡区均可视为由无孔砂浆基质和孔隙水夹杂相组成的两相复合材料,二者的主要区别表现为孔隙率不同。在外荷载作用下,砂浆和界面过渡区的毛细孔隙率及孔隙连通性会发生改变,从而改变混凝土的扩散渗透性能。基于此,该文建立了低应力水平下混凝土中氯离子扩散行为多尺度理论分析方法,获得了混凝土表观扩散系数与外荷载（以体应变表征）及砂浆和界面过渡区当前孔隙率的定量关系。分析所采用的主要参数为砂浆和界面过渡区的毛细孔隙率、无孔砂浆基质和骨料相的力学参数、骨料相和界面过渡区的体积分数、外荷载等。与已有文献数据对比知,该文分析结果与之吻合良好,表明了理论分析方法的合理性与准确性。此外,基于该方法,探讨分析了混凝土微/细观结构对其宏观扩散性能的影响。
英文摘要：
The diffusivity of concrete is closely related to the microstructure which involves the interfacial transition zone （ITZ） between aggregate particles and cement paste at the meso-scale, as well as the microstructure of cement paste itself. At the micro-scale, the cement paste and the ITZ can be assumed to be composed of an intrinsic cement paste phase and a pore-water inclusion, with different porosities. Under external mechanical stress, the porosities and the connectivity of capillary pores within the cement paste and the ITZ will be changed, resulting in the change of the chloride diffusivity of concrete. In this study, a multi-scale analytical method that can predict the chloride diffusivity of concrete subjected to low-level stress is proposed. The quantitative relationship between the apparent diffusion coefficient of concrete and the mechanical stress （herein i.e. the volumetric strain） as well as the current porosities of cement paste and the ITZ is evaluated. The main parameters in the analytical method are the capillary porosities of cement paste and the ITZ, the mechanical properties of the intrinsic cement paste phase and the aggregate, the volume fractions of aggregate and the ITZ, and the mechanical stress. A good agreement between theoretical results and available test data illustrates the reliability and accuracy of the developed analytical approach. Based on the presented analytical method, the effect of micro- / meso-structure of concrete on its apparent diffusivity was investigated.
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