模型再生混凝土二维氯离子扩散细观数值模拟

Meso-level numerical simulation on two-dimensional chloride diffusion in recycled aggregate concrete

摘要:

根据再生混凝土各相介质氯离子(Cl-)扩散率和几何参数建立了数值模型，对模型再生混凝土二维Cl-扩散性进行数值模拟，研究了再生混凝土的Cl-扩散特性。通过变化再生粗骨料取代率、新硬化水泥砂浆扩散率、老硬化水泥砂浆扩散率、老硬化水泥砂浆厚度以及界面过渡区(ITZ)扩散率，对再生混凝土中Cl-扩散性能进行了对比分析。结果表明：模型再生混凝土内部Cl-浓度非均匀分布，Cl-浓度沿着扩散深度波浪式下降，再生粗骨料取代率、水泥砂浆、ITZ等的变化对Cl-浓度的影响随着扩散深度的增加而逐渐变大，且在ITZ处的影响较为明显。

Abstract:

According to the chloride diffusivity and geometric parameter of the five-phase recycled aggregate concrete (RAC), the chloride diffusion characteristics in modeled RAC is numerically simulated. The effect of relevant parameters, i.e., the replacement ratio of recycled coarse aggregate, the diffusivity of new and old hardened cement mortar and the interfacial transition zones, as well as the thickness of old hardened cement mortar on the diffusion properties of RAC is analyzed comparatively. The results obtained from the numerical simulation indicate that the distribution of chloride concentration is non-uniform within the modeled RAC; and the chloride concentration in recycled aggregate concrete declines wavelike along the diffusion depth. Furthermore, the influence of recycled coarse aggregate replacement ratio, cement mortar, ITZ, etc., on the chloride concentration is distinctly increased with the increase of the depth, and more obvious at the ITZ.