Steel in concrete: Part I A review of the electrochemical and thermodynamic aspects

Abstract

The electrochemical and thermodynamic factors influencing the stability of steel reinforcements in concrete are reviewed on the basis of prevailing conditions during the states of passivity, passivity breakdown and the onset of active corrosion. Details of reaction mechanisms characteristic of each of the states are outlined and the areas requiring further studies are defined. The resistivity of the concrete cover—both at the steel/concrete interface and of the bulk concrete matrix—and bulk humidity levels appear in general to be most significant. Special emphasis is given to intermediate humidity levels since these are encountered by normal structuresand they also represent a rather active thermodynamic regime regarding the durability of concrete reinforcements. Factors discussed in connection with the intermediate humidity regime are: (l) the availability of O2, (2) the chloride ion efect and (3) carbonation.