THE "SHOW ME" STATE SHOWS OFF CATHODIC PROTECTION

Missouri is known as the "Show Me" state because of its pragmatic approach to change. But the state can be a national pacesetter when newness offers promising returns. A case in point: Missouri leads North America in using cathodic protection (CP) to extend performance life for salt-contaminated and corroded concrete bridges. Beginning with its first full-scale installation in 1975, Missouri today has 126 CP systems in place or underway, almost half of all CP applications in the U.S. During this time Missouri has stayed abreast of new advancements and refinements in CP technology. Following the pancake anode, the state moved next to a conductive grout method developed by the FHWA and installed in slot and mound designs. Then a different anode was used, a flexible polymeric material enclosing a stranded copper wire core. This system was covered with a latex modified or low slump concrete overlay. In 1986, Missouri began to install and monitor a promising new CP technique in conjunction with an FHWA demonstration program. This system uses a proprietary anode composed of a mixed precious metal oxide catalyst and sintered to a titanium mesh or ribbon form. This ELGARD anode is designed to be compatible within its surrounding concrete environment and can sustain the design current discharge for the life of the rehabilitation--25 years or longer. It can be installed with a wide variety of conventional concrete covers and offers great redundancy in available electrical paths. To date, Missouri has installed this titanium-based anode system on 17 bridges. The state continually monitors and evaluates each of its CP installations.