Permeability of C-S-H

Abstract

Hydrodynamics in calcium silicate hydrates nanopores are crucial to concrete’s durability and confinement performance. Here, Non-Equilibrium Molecular Dynamics simulations of water confined in-between C-S-H layers are reported considering slit pore sizes spanning interlayer and gel pores. These simulations enable the computation of the permeability of C-S-H and the quantification of the boundary conditions associated with the flow. A tensorial formalism is applied to describe this forced flow accounting for the pore wall texture and resulting stick/slip boundary conditions. As for other properties, shear viscosity also shows a significant pore-size dependence at the nanoscale. The adoption of slip boundary conditions and confinement-dependent viscosity is crucial to capturing the water permeability of the C-S-H gel. The fundamental link between self-diffusion and viscosity (following the Einstein–Stokes equation) describes the temperature dependence of hydrodynamics.