Résumé
Atmospheric carbonation is one of the most significant degradation factors in the durability of reinforced concrete structures. It entails the action of CO2 in the atmosphere, which diffuses through the concrete and then dissolves when in contact with the pore solution. This phenomenon induces acidification of the medium, which leads to the dissolution of the hydrates composing the reserve of concrete basicity. Then the pH value abruptly decreases from a value of the order of 13 to one less than 9. It leads to the corrosion of the reinforced bars which are protected with a high pH level. The aim of this work is to build up a physico-chemical modelling of carbonation of cement based materials which enables to predict the drop of the pH value in pore solution, given that the pH value constitutes a pertinent variables in comprehending reinforcement corrosion. A very informative experimental campaign (thermogravimetric analyses, gammadensitometry, mercury intrusion, etc.) is conducted on three different concrete mixes and many cement pastes (with cement CEM I). It is used to clarify the physico-chemical mechanism of carbonation in order to quantify the influence of carbonation on the microstructure and on the hydric state, to calibrate and eventually to validate the model with accelerated carbonation tests.