Durability Design of Concrete Structures

1Carbonation and Induced Steel Corrosion

This chapter treats the first important durability process of concrete materials and structures: the carbonation and the induced corrosion of steel bars in concrete. The carbonation of concrete originates from the reaction between the alkaline pore solution of concrete and the carbon dioxide (CO₂) gas migrating into the pores. The carbonation does not compromise the material properties but decreases the alkalinity of the pore solution, which has an adverse effect on the electrochemical stability of steel bars in concrete. The risk of steel corrosion can be substantially enhanced in a carbonated concrete. This chapter begins with the phenomena of concrete carbonation and its effect on the long‐term durability of concrete materials and structures. Then the detailed mechanisms are presented, according to the state of the art of knowledge, for concrete carbonation and the induced steel corrosion, together with a comprehensive analysis on the main influential factors for these processes. On the basis of the available knowledge, the modeling aspect is brought forth through mechanism‐based and empirical models for engineering use. Since the valid scope and the uncertainty are two fundamental aspects for model application, the critical analysis is given to the models presented and their application. Some basis for durability design against the carbonation and the induced corrosion is given at the end.

1.1 Phenomena and Observations

As concrete ...