MASS-TRANSFER IN INHOMOGENEOUS POROUS-MEDIA UNDER THERMAL-GRADIENTS

A realistic simulation of the coupled heat-and mass-transfer in inhomo geneous porous media requires detailed knowledge of the dominant trans fer mechanisms. Depending on the local temperature and moisture conten t, a description in terms of diffusion or Darcy flow respectively is a ppropriate. However, a simultaneous application of these fundamental p hysical transfer mechanisms is necessary when subjecting complex pore structures like hardening cementitious materials to wide-ranging tempe rature distributions. With rising temperatures, continuing hydration a lso 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 thermodyn amic concepts. The resulting time-space evolution of the state variabl es is described by a set of coupled nonlinear partial differential equ ations. A numerical model of the coupled heat-and mass-transfer as inf luenced by continuing hydration with a temperature-dependent reaction rate is presented, and the results of the mass transfer simulation und er thermal gradients is compared with experimentally determined concen tration distributions obtained on a model system. (C) 1998 Elsevier Sc ience S.A. All rights reserved.