Abstract
Previous work has shown that chloride corrosion threshold increases when steel bar potentials are more cathodic than -200±50 mV (SCE). When corrosion starts at a given location, the steel of the adjacent regions remains in its passive state; therefore corrosion initiation is delayed in those regions due to the negative shift in potential. Introduction of threshold dependence on potential is a critical need for accurate forecasting, as neglecting that phenomenon can lead to erroneously high damage projections. An earlier investigation incorporated this issue in a one-dimensional deterministic model solved by a finite difference method evaluating a partially submerged reinforced concrete column. While the model served to demonstrate feasibility of the concept, damage prediction was found to be highly sensitive to the corrosion activation zone size. As the number of nodes used for the model increased, resulting in smaller activation zones, the total predicted amount of damage at a given age decreased. Examination of the model assumptions suggested that the problem stemmed from neglecting the local resistance of the concrete around the steel bars. An improvement has been developed here by implementing a formulation that accounts for the local resistance polarization associated with the selection of the size of activation zone. The damage projections for the smaller node separation resulted in a finite limiting value. Comparison with a case where the effect of local resistance polarization in the activation zone size is neglected is presented.
