基于第一性原理的氯盐环境下混凝土中钢筋锈蚀特性分析

Analysis on corrosion properties of reinforcement in concrete in chloride environment based on first-principles

为了阐明氯盐环境对混凝土中钢筋锈蚀反应的影响机理,采用基于密度泛函理论(DFT)中的第一性原理,运用CASTEP软件包建立了O2分子与Cl原子在Fe(100)表面的吸附模型,研究了Cl原子的存在对O2分子吸附于Fe(100)表面的吸附能、几何结构和表面电子特性的影响.结果表明,Cl原子的存在会增大O2分子与Fe(100)表面之间的吸附能和O2分子键长,减小O原子之间共价键,从而促使O2分子向基底表面靠近,并使得铁基底更容易失去电子,同时增大了Fe原子层向O原子的电子转移量.因此,Cl原子的存在会导致O2分子与基底Fe原子的相互作用增强,从而促进了O2分子的裂解以及基底表面原子间的成键,进而从微观尺度上证明了氯盐环境会显著促进混凝土中钢筋锈蚀氧化反应.

In order to clarify the influence mechanism in chloride environment on the corrosion reaction of reinforcement in concrete,by using the first-principles based on the density functional theory（ DFT）,the adsorption model for oxygen molecule and chloride atom on the surface of Fe（ 100） was established using the CASTEP software package. The influences of the existence of chloride atom on the adsorption energy,the geometric structure and the electric properties of oxygen molecule were investigated. The results showthat the existence of chloride atom can enhance the adsorption energy between oxygen molecule and Fe（ 100）,increase the bond length of the oxygen molecule and decrease the covalent bond between oxygen atoms,which makes the oxygen molecule closer to the substrate. Besides,the existence of chloride atom also makes the ferrous substrate easier to lose electrons and increases the electron transfer number from iron atom layer to oxygen atom. Therefore,the existence of chloride atom can remarkably enhance the interaction between oxygen molecule and ferrous substrates,promote the splitting of oxygen and the bond formation between atoms on the surface of the substrate,clarifying from micro scale that the existence of chloride environment can promote the oxidation reaction of reinforcement corrosion.