C-S-H凝胶无定型纳米孔隙中NaCl蒸发结晶分子动力学分析

Molecular Dynamics of NaCl Evaporation Crystallization in C-S-H Gel Amorphous Nanopores

氯化钠(NaCl)干湿循环结晶会对水泥混凝土材料产生破坏,现有试验方法存在局限性,很难从纳米尺度对盐结晶破坏机理进行研究。因此本文采用分子动力学方法,针对水泥水化主要微观产物水化硅酸钙(C-S-H)凝胶,研究NaCl在C-S-H凝胶无定型孔隙中蒸发结晶过程和结晶破坏机理。结果表明,本文构建的C-S-H凝胶无定型模型更接近于低密度的C-S-H凝胶模型,NaCl在这个模型孔隙中蒸发结晶遵循两步成核机制,蒸发结晶后的NaCl晶体填充C-S-H凝胶纳米孔隙,会显著降低C-S-H凝胶整体抗拉变形能力,使C-S-H凝胶变脆,这一结论为解释C-S-H凝胶在蒸发结晶作用下产生破坏的现象提供了依据。

The dry and wet cyclic crystallization of sodium chloride(NaCl) can damage cement concrete materials,and the limitations of the existing experimental methods make it difficult to study the salt crystallization damage mechanism from the nanoscale.Therefore,this paper adopted the molecular dynamics method for the main microscopic product of cement hydration,calcium silicate hydrate(C-S-H) gel,to study the evaporation crystallization process of NaCl in the amorphous pores of C-S-H gel and the crystallization damage mechanism.The results show that the C-S-H gel amorphous model constructed in this paper is closer to the C-S-H gel with low density,and the evaporation crystallization of NaCl in the pores of this model follows a two-step nucleation mechanism,and the filling of C-S-H gel nanopores by evaporated crystallized NaCl crystals significantly reduces the overall tensile deformation capacity of C-S-H gel,and makes C-S-H gel brittle,which is a conclusion to this conclusion provides a basis for explaining the phenomenon of C-S-H gel destruction under the action of evaporation crystallization.