Molecular structure and dynamics of water on the surface of cement hydration products: Wetting behavior at nanoscale

• Water droplets have good wettability on CSH, Ca(OH) 2 and AFt surfaces. • The tendency of water droplets to invade the interior of the three substrates is: AFt>CSH>Ca(OH) 2 . • Water molecules mainly interacted by ionic pairs and H-bonds on the CSH and AFt interface while interacted by H-bonds on the Ca(OH) 2 interface. • The tendency of different matrices to restrict the droplet:AFt>CSH>Ca(OH) 2 . The distribution and wettability of water molecules on the surface of different cement hydration products have a close influence on the transport behavior of water in the gel pores of the concrete, thus affecting the durability of concrete. To understand the wetting behavior of water droplets on interfaces of different hydration products (CSH, AFt, Ca(OH) 2 ), the MD method was used to study the wetting properties of water molecules on the interfaces of three matrices. At the nanoscale, the water droplet on the surface of the three substrates shows good hydrophilicity, but there are significant differences in wetting behavior. Water molecules show a relatively stable state on the CSH interface through the interaction of stable Ca-Ow ionic pairs and relatively stable hydrogen bonds. On the Ca(OH) 2 matrix, water molecules almost exist in the form of double water film, and interact with Ca(OH) 2 through the low stability hydrogen bond. For the AFt matrix, water molecules are firstly wetted at the AFt matrix interface in free orientation and movement and finally exist in a relatively stable condition. This work provides a nano-perspective for the wetting properties of water at the interfaces of different cement hydration products.