Utility of Submerged Anodes for Cathodic Protection of Above-Waterline Reinforced Concrete Elements—Part 1: Bulk Zinc Anodes

Reinforced concrete bridge substructures in Florida coastal waters have historically experienced deterioration as a consequence of embedded steel corrosion followed by concrete cracking and spalling. Galvanic anode cathodic protection (GACP), as affected by thermally sprayed zinc for cast-in-place components and zinc mesh jackets for precast ones, has been used to control this corrosion and extend useful service life. In either case, the CP systems are supplemented by a zinc submerged bulk anode (ZnSBA) to reduce current drain from the lower portion of the thermal spray or jacket components. To investigate the extent of any contribution of ZnSBA in protecting the above-waterline zone, two substructures of the Bahia Honda Bridge in the lower Florida Keys were instrumented with ZnSBA only and monitored. The results indicated good polarization and protection of the footers but with protection lessening with increasing elevation on the columns. In addition, the substructures and ZnSBA were modeled using boundary element analysis, and comparison of these projections with field measurements indicated generally good agreement between the two. The utility of a ZnSBA as a stand-alone CP source is discussed.