Ab initio molecular dynamics description of proton transfer at water-tricalcium silicate interface

TL;DR

This study uses ab initio molecular dynamics to explore proton transfer mechanisms at the water-tricalcium silicate interface, revealing protonation, hydroxide formation, and water dissociation dynamics relevant to early hydration processes.

Contribution

First ab initio molecular dynamics simulation of the C3S/water interface, providing detailed insights into proton transfer and surface chemistry during initial hydration.

Findings

Protonation occurs first on oxides with favorable environments.

Proton transfers happen between water and silicates, and water and hydroxides.

Silanol groups are unstable during early hydration stages.

Abstract

For the first time, an ab initio molecular dynamics simulation was performed to describe the C$_3$S/water interface. The simulation shows that oxides with favorable environment are protonated at first, creating very stable hydroxide groups. Proton transfers occur between water and silicates, and between water and hydroxides formed upon water dissociation on the surface. The typical lifetime of these events is on the same timescale than interconversion between Eigen and Zundel ions in bulk water. At the very early stage of the hydration encompassed by our simulation, silanol groups are very unstable and molecular adsorption of water is slightly more stable than dissociative adsorption.