CATHODIC PROTECTION AND TECHNOLOGY FOR PRESTRESSED CONCRETE (WPI - 0510376). FINAL REPORT

A series of experiments has been performed whereby simulated prestressed concrete piling specimens with both continuous and segmented tendons were exposed to seawater. Most of the specimens were admixed with a high level (20 lbs per cu yd) of chlorides as CaCl2. Subsequent to corrosion state characterization under freely corroding conditions, the mid-portion of each specimen was instrumented with an impressed current (potential control) cathodic protection system utilizing a conductive rubber anode. The magnitude of impressed current and its distribution along the embedded steel were monitored as a function of exposure time and level of polarization. Potential distribution for both the continuous and segmented tendons was also measured. The level of cathodic protection was accessed as a function of position along the specimens by the depolarization method. The following conclusions have been reached: (1) Current to the tendon decreased with time during the first 30 days (approximate) and was relatively constant thereafter. (2) Cathodic protection was readily achieved upon the steel directly beneath the anode; however, both potential and protection level attenuated rapidly (within a few centimeters) above the anode. The attenuation was less pronounced for a specimen without admixed chlorides compared to ones with these chlorides. This suggests that cathodic protection utilizing an impressed current anode in the splash zone may not provide long term protection once chlorides accumulate in the concrete above the anode, as is likely to occur in an open water location (Monroe County, for example). On the other hand, this should not be as significant in sheltered water applications such as the Intercoastal Waterway.