ABSTRACT
This chapter shows the diversity of results obtained on concrete according to the techniques chosen; determine if these techniques are applicable to high performance concretes, and, in the affirmative, expose the general tendency to noticeable variations for normal and high performance concrete. It examines the effect of the composition of a concrete upon its air permeability. Most researchers recognize that the water acts on the structure of the concrete, in which it percolates, either by dissolution of the hydrates (portlandite mainly) or opposingly by provoking a continuation of hydration of the anhydrides. It would be possibly more important to determine the phenomena relative to the fluid transfer, which establish themselves in the concrete in use, and to measure the corresponding coefficients of permeability (or diffusion). The chapter illustrates well the multiplicity of the transfer processes of fluids in a real construction.
