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为了在原子水平上再现硅酸盐水泥的主要水化产物水化硅酸钙的结构,以Hamid模型为基础建立初始结构,采用分子动力学方法这一物质结构研究的新手段,模拟低钙比的Ⅰ型水化硅酸钙[Ca4Si6O14(OH)4·2H2O,C-S-H(Ⅰ)]的结构;根据模拟结果,比较分析水合硅酸钙晶体与无定形水化硅酸钙在结构上的异同,并且通过与实验数据的比较验证模拟结果的可靠性。模拟结果表明:水合硅酸钙晶体的结构长、短程确实都有序,而其无定形态的C-S-H(Ⅰ)只存在近程有序的结构特点,因为后者中Ca—O、Si—O、O—O及Si—Si等原子对的径向分布函数随着原子间距的增大而逐渐趋于1;C-S-H(Ⅰ)的基本结构单元为硅氧四面体,并且Si的最近邻Si数目为2,即硅氧四面体以Q2的形式连接而呈链状;模拟得到的Si与O、Ca与O的间距分别为0.162nm和0.264nm,Si的O配位数为4,这些结构参数基本与实验值相符合,说明模拟结果能够再现C-S-H(Ⅰ)的结构。
In order to reproduce the structure of hydrated calcium silicate, the main hydration product of Portland cement, at the atomic level, the initial structure was established based on the Hamid model. By means of molecular dynamics method, a new method of material structure study, Type calcium silicate hydrate [Ca4Si6O14 (OH) 4 · 2H2O, CSH (Ⅰ)]. According to the simulation results, the similarities and differences between the hydrated calcium silicate crystals and the amorphous calcium silicate hydrate were analyzed. The reliability of simulation results is verified by comparison with experimental data. The simulation results show that the structure of hydrated calcium silicate crystals is indeed ordered in both long and short paths, while the CSH (Ⅰ) in amorphous state exists only in the short-range order structure because Ca-O, Si-O , O-O and Si-Si and other atomic pairs of the radial distribution function with the increase of the distance between the atoms gradually become 1; CSH (Ⅰ) the basic structural unit is a silicon tetrahedron, and Si the nearest Si number Is 2, that is, the silicon tetrahedron is connected in the form of Q2 to form a chain; the distances between Si and O, Ca and O obtained by the simulation are respectively 0.162 nm and 0.264 nm, and the O coordination number of Si is 4, and the structural parameters The experimental results agree well with the experimental data, which shows that the simulation results can reproduce the structure of CSH (Ⅰ).