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CATHODIC PROTECTION FIGURE 6 bound lanes were protected, and the northbound lanes were left unprotected as a control. The two halves were sepa- rated by an open joint. As with the West- way Boulevard Bridge, a complete de- lamination survey was not conducted, but the wearing surface of the deck on both sides of the bridge showed no visible sign of damage. 1V\MZVIT KWUXWVMV\[ WN \PM ZMK\QÅMZ M`PQJQ\ML [QOVQÅKIV\ KWZZW[QWV J]\ \PM unit was still operating properly. Table 3 shows ICCP currents and voltages taken on October 1, 2009. The currents shown in Table 3, equal to 0.56 and 0.33 mA/ft2 m2 considered typical. The voltages for both zones are also considered typical. The potentials recorded by all four reference electrodes appear to be normal. Potential Decay Test, Columbia Road Bridge Polarizations at the Columbia Road Bridge were determined using the refer- ence electrodes embedded in Zones 1 and 2, and at four test points located on the surface of the concrete along the west curb. As with the Westway Boulevard Bridge, polarizations from the surface test points were determined using a portable SCE. Potential decays over a 4-h test period are shown in Figure 5. Potential decays recorded at embedded Ag/AgCl reference electrodes are shown as dotted lines, and decays recorded at surface test points using SCEs are shown as solid lines. The measured potential decays at the Columbia Road Bridge indicate protec- tion in accordance with the design criteria at all of the test points. Average potential decay was 176 mV. A visible difference was expected be- tween the protected and unprotected lanes of this bridge, thus demonstrating the effectiveness of CP; however, there NACE International, Vol. 51, No. 11 (6.0 and 3.6 mA/ ) for Zones 1 and 2 respectively, are TABLE 4 Potential survey on curbs at Columbia Road Bridge Protected Curb 108 Number of potentials Average potential Potentials < –276 mV (corrosive) Potentials > –126 mV (not corrosive) was no visible difference between the southbound and northbound lanes of the bridge. The original data taken when ICCP was installed did not survive, but it is probable that this bridge was not un- LMZOWQVO [QOVQÅKIV\ KWZZW[QWV I\ \PM \QUM of installation, and therefore may not have been a good candidate for com- parative testing. Unprotected Curb Areas, Columbia Road Bridge Both the protected southbound and the unprotected northbound lanes of the Columbia Road Bridge have a 6-in (152- mm) high by 16-in (406-mm) wide curb area adjacent to the driving lanes. During the testing of the ICCP system, a very significant difference was noticed be- tween the two curb areas. The curb ad- –126 mV 5 79 Unprotected Curb 108 –242 mV 47 15 jacent to the protected southbound lanes showed very little damage due to corro- sion, whereas the curb adjacent to the unprotected northbound lanes showed extensive spalling and delamination. Figure 6 shows this difference. It was speculated that the curb area adjacent to the protected lanes was receiving some protective current, even though anodes were not directly installed on this area. Damage due to corrosion might have occurred on the unprotected curb since the curbs were not overlaid during reha- bilitation, which allowed chloride con- tamination to increase in the concrete during the years since installation. Potential decay tests were conducted on the curb adjacent to the protected southbound lanes to see if that curb was receiving current from the ICCP system. November 2012 MATERIALS PERFORMANCE 35 Columbia Road Bridge median curb.