Water transport in the nano-pore of the calcium silicate phase: reactivity, structure and dynamics

Abstract

Reactive force field molecular dynamics was utilized to simulate the reactivity, structure and dynamics of water molecules confined in calcium-silicate-hydrate (C-S-H) nano-pores of 4.5 nm width. Due to the highly reactive C-S-H surface, hydrolytic reactions occur in the solid-liquid interfacial zone, and partially surface adsorbed water molecules transforming into the Si-OH and Ca-OH groups are strongly embedded in the C-S-H structure. Due to the electronic charge difference, the silicate and calcium hydroxyl groups have binomial distributions of the dipolar moment and water orientation. While Ca-OH contributes to the Ow-downward orientation, the ONB atoms in the silicate chains prefer to accept H-bonds from the surface water molecules. Furthermore, the defective silicate chains and solvated Caw atoms near the surface contribute to the glassy nature of the surface water molecules, with large packing density, pronounced orientation preference, and distorted organization. The stable H-bonds connected with the Ca-OH and Si-OH groups also restrict the mobility of the surface water molecules. The significant reduction of the diffusion coefficient matches well with the experimental results obtained by NMR, QENS and PCFR techniques. Upon increasing the distance from the channel, the structural and dynamic behavior of the water molecules varies and gradually translates into bulk water properties at distances of 10-15 Å from the liquid-solid interface.

Fabrication of large-pore mesoporous Ca-Si-based bioceramics for bone regeneration

“…Therefore, LPMSC-1 and LPMSC-2 could bind rhPDGF-BB via hydrogen bonds. [26][27][28][29] However, there was no Si-OH on the surface because LPMSC-3 was completely transformed…”

Role of porosity on the stiffness and stability of (001) surface of the nanogranular C–S–H gel

“…In the work of Hou et al [68], it is shown that a C-S-H surface is highly reactive, and hydrolytic reactions occur in the solid-liquid interfacial zone. They explain that a part of the adsorbed water molecules transforms into the Si-OH and Ca-OH groups.…”

The Role of Water on C-S-H Gel Shear Strength Studied by Molecular Dynamics Simulations

“…At 5 Å, the shear strenght has dropped to as much as 10% of the ideal contact case, and the system loses all the cohesion under shear strain at 1 nm separation. It is interesting to note that for such a small distance the water is considered to present confined dynamics, with lower mobility than bulk water (Bonnaud et al 2010;Hou et al 2015). However, in terms Rev.…”