Mass transfer in inhomogeneous porous media under thermal gradients Original Research Article

A realistic simulation of the coupled heat- and mass-transfer in inhomogeneous porous media requires detailed knowledge of the dominant transfer mechanisms. Depending on the local temperature and moisture content, a description in terms of diffusion or Darcy flow respectively is appropriate. However, a simultaneous application of these fundamental physical transfer mechanisms is necessary when subjecting complex pore structures like hardening cementitious materials to wide-ranging temperature distributions. With rising temperatures, continuing hydration also influences the moisture distribution in an increasingly important manner in addition to the transport phenomena. The description of the relevant transport processes can be realistically handled by thermodynamic concepts. The resulting time-space evolution of the state variables is described by a set of coupled nonlinear partial differential equations. A numerical model of the coupled heat- and mass-transfer as influenced by continuing hydration with a temperature-dependent reaction rate is presented, and the results of the mass transfer simulation under thermal gradients is compared with experimentally determined concentration distributions obtained on a model system.