COMPUTATION OF REINFORCING STEEL CORROSION DISTRIBUTION IN CONCRETE MARINE BRIDGE SUBSTRUCTURES

Corrosion conditions prevalent in the partially submerged, reinforced concrete substructures of marine bridges were incorporated into a computer model. The modeled system was an axisymmetric cylindrical column with a rebar cage along its entire length. Inputs included column and cage dimensions, the size of the portion of the rebar cage in an active state, the concrete resistivity and oxygen diffusivity distributions along the column, the polarization characteristics of the steel, and the external oxygen concentration. A finite difference model was used to compute the distribution of electrical potential and oxygen concentration. From those results, the distribution of oxygen consumption and corrosion current densities over the rebar cage were obtained. Cases addressing various dimensions and various distributions of oxygen diffusivity and concrete resistivity were analyzed. Results showed a tendency for greatest corrosion near the top of the active zone. Relative changes in oxygen diffusivity were found to have a greater impact on corrosion activity than comparable relative changes in concrete resistivity. Implications for marine substructures were examined.