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混凝土类水泥浆复合材料中各种尺度的孔隙,如凝胶孔、毛细孔、掺入的气体气泡以及微裂纹等影响着氯离子的扩散性能。孔隙结构参数(如孔隙率)在外荷载作用下会产生变化,进而影响了水泥浆体中氯离子扩散性能。外荷载作用对氯离子扩散行为的影响,可以等效为外荷载所引起的孔隙率的改变对氯离子扩散性能的影响。从微观角度出发,将饱和水泥浆体看作由水泥浆体基质(其孔隙率为零)和孔隙水夹杂相所组成的两相复合材料介质。基于弹性力学理论推导并获得了饱和水泥浆体达到其强度前(即未产生新裂纹前)当前孔隙率与材料初始孔隙率及体应变之间的定量关系,得到了水泥浆体中氯离子扩散系数与这些参数的定量关系。基于Fick第二定律分析了外荷载(体应变)和孔隙率变化对氯离子扩散性能的影响。研究表明:氯离子在饱和砂浆中的扩散系数随孔隙率增大而显著增大;氯离子在砂浆中的扩散系数随压缩体应变的增大而减小,随拉应变增大而增大。
Various scale pores in concrete grouting composites, such as gel pores, pores, gas bubbles mixed with microcracks and the like, affect the diffusion performance of chloride ions. Pore structure parameters (such as porosity) will change under the action of external load, thus affecting the chloride diffusion in cement paste. The influence of external load on the chloride ion diffusion behavior can be equivalent to the effect of the change of the porosity caused by the external load on the chloride ion diffusion performance. From a microscopic point of view, saturated cement paste is considered as a two-phase composite material composed of cement paste matrix with zero porosity and pore water inclusion. Based on the theory of elastic mechanics, the quantitative relationship between the current porosity and the initial porosity and the bulk strain of the saturated cement paste before it reaches its strength (that is, before the new crack is generated) is deduced and the chloride ion diffusion Quantitative relationship between these parameters and these parameters. Based on Fick’s second law, the effects of external load (bulk strain) and porosity on the chloride diffusion were analyzed. The results show that: the diffusion coefficient of chloride ions in saturated mortar increases significantly with the increase of porosity; the diffusion coefficient of chloride ion in mortar decreases with the increase of compressive strain, and increases with the increase of tensile strain.