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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。
The diffusion and permeability of concrete is closely related to its microstructure (including the interface transition zone between coarse aggregate particles and mortar on the mesoscopic scale and the microstructure of the mortar itself). At the microscopic scale, both the mortar and the interface transition zone can be regarded as two-phase composite materials composed of non-porous mortar matrix and pore water inclusion phase, the main difference between the two is porosity. Under the action of external load, the capillary porosity and pore connectivity of mortar and interfacial transition zone will change, which will change the diffusion and permeability of concrete. Based on this, a multi-scale theoretical analysis method of chloride ion diffusion in concrete under low stress level was established. The apparent diffusion coefficient of concrete and external load (characterization of body strain) and the current porosity of mortar and interface transition zone were obtained relationship. The main parameters used in the analysis are the capillary porosity of mortar and interface transition zone, the mechanical parameters of non-porous mortar matrix and aggregate phase, the volume fraction of aggregate phase and interfacial transition zone, and the external load. Compared with the existing literature data, the result of the paper is in good agreement with the results of the analysis, indicating the rationality and accuracy of the theoretical analysis. In addition, based on this method, the influence of concrete micro / meso structure on its macroscopic diffusion properties was analyzed.