5. Conclusions

Contrary to popular belief, the surface of concrete is far from inert. In addition to mechanisms, such as hydration, induced by the very nature of cement, the extreme surface of concrete is a site of particular exchange between the cementitious matrix and its environment (water, ionic compounds, gases and micro-organisms).

The kinetics of all these reactions involve various time periods, depending on the reaction under consideration: from a few hours for hydration of the main mineral phases at the extreme surface, to a few days for phenomena such as efflorescence, and up to several months or years for phenomena linked to carbonation, leaching or the growth of micro-organisms.

The reactivity of concrete surfaces should therefore not be considered negligible. Indeed, even if certain phenomena seem to affect only the aesthetics of concrete...