This paper has demonstrated that the degree of saturation and the fluids wetting properties play an important role in controlling diffusive transport in porous media. In general, relative diffusivity data can be described by simple third order polynomial functions over a significant range of pore saturation. As a result relative diffusivity curves can easily be incorporated into computer simulations describing the ingress of chloride ions or the egress of carbon dioxide in concrete. Clearly, better predictions of the service life of the building materials may then be made since most estimates of service life are based on the case where the pore space is fully saturated (in the case of chloride diffusion). For the case of cementitious materials, the fluids modeled in this paper are somewhat ideal since the interaction of the fluid with the solid is ignored (i.e. dissolution, precipitation and chemical reactions). Further the transport of chlorides should take into account absorption in the solid.
It is also important to consider that saturation may not always be a bulk property and, in general, depends on depth of penetration of the fluid in the porous medium. For instance, near the surface of a porous medium the degree of saturation can be highly variable depending on environmental conditions. To correctly predict diffusive transport in porous media the modeler must take into account weather conditions and wetting-drying cycles. Future research includes examination of hysteresis effects associated with wetting-drying cycles, the role of capillary transport in the ingress of materials in porous media, and the case where the molecular species is not limited to move in a single phase.