In recent years, an increase in the number of structures
presenting symptoms of premature damage has taken place
due to the action of different aggressive processes. This has
made it necessary to improve the scienti®c knowledge of the
physical and chemical mechanisms, which deteriorate the
concrete, as much as of the procedure to evaluate its durabil-
ity, in order to mitigate the high cost of repairing and main-
tenance of these structures. The processes that affect the
durability of concrete are mostly related to its porous struc-
ture, which determines the interaction between concrete and
its environment. Pores and capillaries in the interior of
concrete will propitiate destructive processes, which
commonly start on the surface. Aggressive agents are
carried through the porous structure constituted by channel
pores and ®ssures of different dimensions. Distribution and
size of pores have a particular in¯uence over the type and
celerity of liquids and gases means of transport through the
structure. According to size, pores can be sorted in