Now, after applying these averaging operators, we obtain the microscopic balance equation. For instance we have the solid skeleton mass balance equation. These are the accumulation terms, already partly developed, and the flux terms. And here I have a term which takes into account hydration or dehydration.
Then we have the mass balance equation for the air phase, again we have the accumulation terms, for instance things change at a degree of saturation, change of temperature, influence of the solid deformation, influence of the compressibility of the gas phase, then we have the diffusional flux.