Chloride threshold for reinforcement corrosion has been found to be very variable in function of several material and environmental characteristics. Regarding carbonation, the corrosion onset is associated to the arrival to the rebar of the carbonation front. In both cases it is usually neglected in the calculations the geometrical fact of considering the whole perimeter of the rebar. Regarding the corrosion propagation, the evolution can be modelled in function of the concrete resistivity which based in concrete water saturation gives the corrosion rate. Variation of the nominal values of the diffusion coefficient of chlorides and carbon dioxide, of the chloride threshold and of the corrosion rate make very uncertain the predictions. In present paper is presented an attempt to reduce the uncertainties but a more thorough analysis of the physical processes happening during chloride depassivation by integrating the initiation to the propagation period and calculating the probability of failure due to the arrival of a certain chloride threshold or the carbonation front. Then the progress of the corrosion is taken as the parameter to define the most technically suitable probability of depassivation. The corrosion rate developed is made a function of the diffusion coefficient and of the saturation degree through their relation to the concrete resistivity. An example is commented to illustrate the approach.

The authors would like to acknowledge the financing of the Ministry of Science and Innovation for the INGENIO 2010- CONSOLIDER Project on “Safety and Durability of Structures: SEDUREC”.

Trabajo presentado en el 8th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-8), celebrado en Toledo (España), del 10 al 14 de marzo de 2013