title: Anomalous composition-dependent dynamics of nanoconfined water in the interlayer of disordered calcium-silicates.
abstract: With shear interest in nanoporous materials, the ultraconfining interlayer spacing of calcium-silicate-hydrate (C-S-H) provides an excellent medium to study reactivity, structure, and dynamic properties of water. In this paper, we present how substrate composition affects chemo-physical properties of water in ultraconfined hydrophilic media. This is achieved by performing molecular dynamics simulation on a set of 150 realistic models with different compositions of calcium and silicon contents. It is demonstrated that the substrate chemistry directly affects the structural properties of water molecules. The motion of confined water shows a multi-stage dynamics which is characteristic of supercooled liquids and glassy phases. Inhomogeneity in that dynamics is used to differentiate between mobile and immobile water molecules. Furthermore, it is shown that the mobility of water molecules is composition-dependent. Similar to the pressure-driven self-diffusivity anomaly observed in bulk water, we report the first study on composition-driven diffusion anomaly, the self diffusivity increases with increasing confined water density in C-S-H. Such anomalous behavior is explained by the decrease in the typical activation energy required for a water molecule to escape its dynamical cage.
authors: Concrete Sustainability Hub, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors: Mohammad Javad Abdolhosseini
authors: MJ
authors: Qomi
authors: Concrete Sustainability Hub, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors: Mathieu
authors: M
authors: Bauchy
authors: Concrete Sustainability Hub, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors: Franz-Josef
authors: FJ
authors: Ulm
authors: Concrete Sustainability Hub, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors: Roland J-M
authors: RJ
authors: Pellenq