阳离子对C-S-H凝胶孔内氯离子扩散影响的分子模拟

Molecular Simulation of Chloride Ion Diffusion Performance in C-S-H Pores under Influence of Different Cations

关键词:  分子动力学  水化硅酸钙  氯离子扩散  阳离子  吸附能力

Key words:  molecular dynamics  calcium silicate hydrate  chloride ion diffusion  cation  adsorption capacity

摘要:

基于分子动力学方法，探究了4种阳离子（K⁺、Na⁺、Ca²⁺、Mg²⁺）对氯离子在水化硅酸钙（C-S-H）凝胶孔中扩散行为的影响机理.结果表明：C-S-H对氯离子的吸附量与其对阳离子的吸附能力相关；Ca²⁺和Mg²⁺可以促进氯离子的吸附，使C-S-H中的表面钙容易脱附进入溶液，延长氯离子和孔隙水的空间相关性，导致氯离子周围形成多层水合壳，降低其扩散能力；在被C-S-H层吸引的阳离子以及水分子的共同作用下，4种溶液中C-S-H凝胶孔中的氯离子扩散系数大小依次为KCl>NaCl>CaCl₂>MgCl₂.

Abstract:

Based on the molecular dynamics simulation， the effects of four cations（K⁺， Na⁺， Ca²⁺， Mg²⁺） on the diffusion behavior of chloride ions in the calcium silicate hydrate（C-S-H） pores were investigated. It is found that adsorption capacity of C-S-H for chloride ions is related to its adsorption capacity for cations. Ca²⁺ and Mg²⁺ can promote the adsorption of chloride ions， and the desorption of surface calcium in C-S-H can be easily facilitated into the solution， in which the spatial correlation between chloride ions and pore water is prolonged， resulting in the presence of multiple layers of hydration shells around chloride ions and the reduction of the diffusion ability. Under the combined actions of cations attracted by the C-S-H layer and water molecules， the ranking of diffusion coefficients of chloride ions in C-S-H pores in four solutions is KCl > NaCl > CaCl₂ > MgCl₂.