Molecular Simulation on Cement-Based Materials by Dongshuai Hou

Author:Dongshuai Hou
Language: eng
Format: epub
ISBN: 9789811387111
Publisher: Springer Singapore

Surface and channel water organization can be well described by the atomic density contours projected in the surface plane. The triangular trajectories of Si–O tetrahedron are used as the reference positions for analysis. The trajectories of the water molecules of the first three peaks in the Ow intensity are recorded in Fig. 5.6. The triangular contours with silicon in the center are the projections of the bridging silicate tetrahedrons, which are taken as the reference positions for the water trajectories. As shown in Fig. 5.6a, the channel water molecules have well-ordered structures and the trajectories show that they are distributed in a line along the silicate chain extension (b axis). As shown in Fig. 5.6a, since few trajectories overlap two neighboring water molecules in different silicate channels, it is believed that the mobility of type 1 is relatively slow and no position exchange occurs. In the upper layer (Fig. 5.6b), type 2 water molecules are concentrated near the ONB atoms of the silicate tetrahedron and the Ca atoms, indicating the strong electronic interaction between water molecules and Ca, ONB atoms. At the distance away from the Ca and the silicate tetrahedron, the contours become less ordered and exchanges between the water molecules occur frequently. The third density map (Fig. 5.6c) exhibits the arrangement of the surface water. The less well-ordered surface water layer is also a transition zone, above which the ordered organization is difficult to be observed. The atomic trajectories from the bottom to the top layers apparently show that water molecules transform from orderly organized channel water to disordered bulk water.

Fig. 5.6Water molecules trajectories of the tobermorite and the water interface: a type 1 water molecules; b type 2 water molecules; c surface water molecules

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