## 3 Results and Discussion  
### Local Microstructure Evolution  
For research into the impacts of varying interfacial water molecule contents on the C-S-H/SiO\({}_{2}\) system, the changes in the \(z\)-axis direction sizes of four models with varying interface water-layer thicknesses (0 A, 1 A, 3 A, and 5 A) after equilibration were counted, as shown in Figure 2. Figure 2a depicts the initial and balance sizes of the C-S-H/SiO\({}_{2}\) model along the \(z\)-axis for varying water-layer thicknesses. The size of the C-S-H/SiO\({}_{2}\) model increased gradually as the interfacial water content rose. However, the change in the C-S-H/SiO\({}_{2}\) model's structural size was inconsistent with the amount by which the interfacial water layer thickened. Figure 2: (**a**) The initial and balance sizes for the C-S-H/SiO\({}_{2}\) model along the \(z\)-axis for varying water-layer thicknesses; (**b**) the differential size between the initial model and the balanced model. The differential size between the initial model and the balanced model is presented in Figure 2b. It is evident that when the interfacial water layer thickened (increasing from 0 A to 1 A), the variation in the structure size was less than 1 A, and the differential size between the initial model and the balanced model was 0.66 A. When the interfacial water layer thickened (increasing from 0 A to 3 A and 5 A), the differential sizes between the initial model and the balanced model were 1.32 A and 1.96 A, respectively. The optimized water-layer thickness changed from 1 A, 3 A, and 5 A to 0.34 A, 1.68 A, and 3.04 A. In order to disclose the mechanism by which the interfacial water molecule content affects the microstructure of C-S-H/SiO\({}_{2}\), this research analyzed the evolution of interfacial water molecules, and the evolution of Ca\({}^{2+}\) ions at the C-S-H surface region. A detailed analysis follows. (1) Evolution of interface H\({}_{2}\)O molecules  
Figure 3 is the distribution of the interfacial H\({}_{2}\)O molecules with varying contents at the X\(-\)Z planar in the C-S-H/SiO\({}_{2}\) model. As depicted in Figure 3a, when 1 A-thick interfacial water molecules were introduced, the interfacial water molecules progressively invaded the C-S-H structure. Based on the [PERSON] theory, water molecules could fill the solid's pits on its rough surface, and the C-S-H surface's hydrophilic nature allowed water molecules to diffuse on its surface [22; 23]. As revealed in Figure 3b,c, when the interfacial water layer thickened (increasing from 1 A to 5 A), the numerous molecules of H\({}_{2}\)O formed clusters easily, while exhibiting a high mobility [24] and diffusion coefficient [25]. As a result, the number of H\({}_{2}\)O molecules that invaded increased gradually. Because of the invasion of H\({}_{2}\)O molecules, the change sizes of the C-S-H/SiO\({}_{2}\) model were smaller than the change in the water molecule thickness. As more H\({}_{2}\)O molecules invaded the C-S-H, the difference between the initial and balance sizes of the model structure increased, as the interfacial water layer thickened. This result is consistent with the variation law of the structure size presented in the previous paper (as shown in Figure 2). The interfacial water molecule evolution law has a similarity to the conclusion obtained by [PERSON] et al. [26], suggesting that water molecules can impact structure size by filling interfacial molecular voids. (2) Ca\({}^{2+}\) ion evolution at the surface region of C-S-H  
For the C-S-H/SiO\({}_{2}\) system with varying interfacial water contents, Figure 4 depicts the spatial distribution of Ca\({}^{2+}\) ions at the surface region of C-S-H.