Molecular dynamics study the structure, bonding, dynamic and mechanical properties of calcium silicate hydrate with ultra-confined water: Effects of nanopore size

Abstract The properties of water ultra-confined in the calcium-silicate-hydrate (C-S-H) affect the mechanical properties and durability of concrete. In this paper, the structure, bonding, dynamics, as well as mechanical properties of C-S-H with ultra-confined water were characterized based on molecular dynamics simulations. The results suggest that the nanopore size has a significant impact on the distribution of water molecules, coordination number of Si-Ow and Ca-Ow and H-bonds. In terms of dynamic features, the penetration of water may weaken the stability of these chemical bonds. The movements of water and Ca, on the other hand, were restricted by various chemical interactions as well as the ultra-confinement environment and the diffusion behavior of water in the nanopore less than 1 nm is isotropic and quasi-two-dimensional. As the increase of nanopore size, the mechanical attributes of C-S-H decrease remarkably and the C-S-H is more easily to be damaged since the increasing of water reduces the cohesion of C-S-H and increases its brittleness. Hopefully, this study could provide some new insights into the characteristics of C-S-H with ultra-confined water.