Molecular Dynamics Study of Water Molecules in Interlayer of 14 Å Tobermorite

Abstract

The molecular structure and dynamics of interlayer water of 14 Å tobermorite are investigated based on molecular dynamics (MD) simulations. Calculated structural parameters of the interlayer water configuration are in good agreement with current knowledge of the refined structure. The MD simulations provide detailed information on the position and mobility of the hydrogen and oxygen of interlayer water, as well as its self-diffusion coefficient, through the interlayer of 14 Å tobermorite. Comparison of the MD simulation results at 100 and 300 K demonstrates that water molecules in the interlayer maintain their structure but change their mobility. The dominant configuration and self-diffusion coefficient of interlayer water are obtained in this study.

Advances in understanding hydration of Portland cement

“…Youssef et al [151] showed that the non-bridging oxygen atoms on the disordered silicate chains orient the hydrogen atoms of the interfacial water molecules toward the calcium-silicate layers, making the C-S-H nano-pore space hydrophilic. The orientation of water molecules in the interlayer of 14 Å tobermorite was obtained by molecular dynamics [152]. The characterization of water confined at ambient temperature inside a C-S-H grain (intragranular) and between C-S-H grains (intergranular) for different relative humidities at 300 K was done by Bonnaud et al [153].…”

Multi-scale modeling of the chloride diffusivity and the elasticity of Portland cement paste

“…But a distinction must be made between interlayer water, surface water and capillary or bulk water [76]. The auto-diffusion coefficient of interlayer water within the 9 to 14 Å layers of the crystalline structure of tobermorite, a C-S-H analogue, has been evaluated to 1.4 to 6.8×10 −11 m 2 /s from MD simulations [76][77][78][79] and 2.6 × 10 −11 m 2 /s from NMR experiments [80], which is about two orders of magnitude smaller than the value for bulk water equal to 2.3×10 −9 m 2 /s. The auto-diffusion coefficient of surface adsorbed water, located within less than 1nm to the C-S-H surface, has been estimated from 4.5 × 10 −10 to 1.2 × 10 −9 m 2 /s [76,79,80] i.e.…”