Reinforcing bars--Cathodic protection

Experiments were conducted to determine the effectiveness of cathodic polarization on simulated concrete piles containing unstressed continuous and segmented tendons exposed to sea water. Conductive rubber was used as anode material. Corrosion of the steel was enhanced by admixturing calcium chloride during concrete pouring. The specimens were cathodically polarized at constant potentials ranging from -0.72 to -1.10 V(sce). Current on and instant off potentials were monitored along the specimen height at different water levels. The four hour potential decay criterion was used to determine if cathodic polarization was effective. Protection was achieved at locations where instant-off potentials were more negative than -0.79 V(sce). Polarization was never obtained above the anode. Also, the possibility of protecting a structure containing discontinuous steel was investigated. The results are discussed within the context of protecting actual marine pilings from corrosion.

Experiments were conducted on a simulated reinforced concrete bridge deck to test different anodes as part of a cathodic protection system. Both carbon based and titanium based anodes were tested. All the anodes were driven at predetermined current densities. Current off polarized potentials of steel and anode were monitored over six months. After this period, cores were extracted from slabs containing a part of anode and steel and then broken at the anode-concrete and steel-concrete interface to measure the pH at these interfaces. Differences in the pH values at the anode-concrete interface were compared to determine the performance of the different anodes. Carbon based anodes operated at a higher potential and produced anode corrosion products of lower pH when compared to titanium based anodes.