混凝土中氯离子扩散纳米通道紧缩性和曲折性影响的分子动力学模拟  

Molecular dynamics simulation of chloride diffusion in concrete considering constrictivity and tortuosity of nanochannels

作　　者：李万金[1] 郭力[1] 高阳[1] 洪俊[1] 

机构地区：[1]东南大学江苏省高校工程力学分析重点实验室,南京210096

出　　处：《东南大学学报（自然科学版）》2015年第1期109-114,共6页Journal of Southeast University：Natural Science Edition

基　　金：国家重点基础研究发展计划(973计划)资助项目(2009CB623202);国家自然科学基金资助项目(11302049;51478108)

摘　　要：结合宏观和微观模型研究了混凝土中纳米通道紧缩性和曲折性对氯离子扩散系数的影响.采用分子动力学方法模拟了氯离子在纳米通道中的输运过程,给出了紧缩性和曲折性影响输运过程的微观机理,结合宏观Fick定律统计分析了模拟结果,得出了紧缩性和曲折性对氯离子扩散系数的影响程度.结果表明,通道壁面结合氯离子影响孔隙液中的粒子分布,使得壁面附近形成吸附自由氯离子的正电层,降低了氯离子的扩散速度;结合氯离子浓度越大,氯离子扩散系数越小.同时,通道壁面原子作用势影响孔隙液中粒子的分布,在壁面附近形成有序的粒子层;通道宽度越大,氯离子扩散系数越大.曲折的通道会强制改变氯离子的输运方向,降低氯离子的扩散系数.The effects of constrictivity and tortuosity of nanochannels on chloride diffusivity in concrete are studied with macro- and micro-scale models. Chloride diffusion processes in concrete nanochannels are simulated with the molecular dynamics method. Correspondingly, microscopic mechanism of effects of constrictivity and tortuosity is obtained. Fick＇s law is adopted to analyze the simulated results, which clarifies the effect degrees of constrictivity and tortuosity on chloride diffusivity. The results show that ions distribution in pore fluid is affected by bound chlorides in nanochannel walls, leading to formation of positron layers which adsorb free chlorides and reduce their diffusion rate. The larger the bound chloride concentration, the smaller the chloride diffusivity. Atomic potentials of nanochannel walls also affect ions distribution. As nanochannel width increases, chloride diffusivity is larger. In tortuous nanochannel, the transport direction of chlorides can be changed, which reduces their diffusion rate.

关 键 词：混凝土纳米通道 氯离子扩散 紧缩性 曲折性 

分 类 号：O35[理学—流体力学]