Multi-Zone Cathodic Protection Monitoring for Bridge Applications

Keywords:

Cathodic Protection, Multi-Zone Rectifiers, Bridge Rehabilitation, Remote Monitoring, Reinforced Concrete

 Abstract:

The highway bridge infrastructure includes a number of structures in need of replacement or significant rehabilitation work.  The respective state’s departments of transportation bear the primary responsibility for the integrity and safety of the nation’s bridges.  These departmental budgets are under significant strain nationwide and this is affecting the challenges involving corrosion prevention on these structures in several ways:  First, an increasing number of bridges are undergoing “life-extending rehabilitation” rather than replacement due to budget issues.  This often involves the introduction of impressed current cathodic protection systems for encased rebar when deck replacement is necessary.  Second, the ever-tightening budgets have resulted in far less personnel available with the knowledge and responsibility to assure proper levels of protection are maintained; and third, increasing public scrutiny and concern regarding bridge safety.  In the State of Missouri, the responsibility for oversight of the design, implementation, and on-going operation of the cathodic protection systems in use on all of the bridge assets in the system falls on a single individual, the “Organizational Performance Engineer”.  This engineer relies on MoDOT field personnel who lack training in the area of cathodic protection for the acquisition of all operational data.  The data is often incomplete and there are numerous opportunities for interjection of human error.  Additionally, the field sites from which the data is acquired are often in very dangerous highway locations, making data acquisition both difficult and hazardous.  These impressed current systems are configured as multiple “Zones” at each site, with each zone producing a voltage, current, and structure to substrate value.  As each site could have anywhere from 4 zones to 10 zones, a cost effective way to accurately acquire all of this data in an organized manner and on a timely schedule provided a unique challenge.  Standard GSM remote monitoring equipment was designed into a 5-zone (15 channel), “Bridge Zone Monitor System” allowing each zone to be accessed as a discreet site while sharing the communication system with the other zones at the site.  This system produces a safe, accurate, cost effective and timely solution to the problem of acquisition of the field data from the MoDOT bridge sites.  This increases the effectiveness of the limited personnel available for the operational integrity of the bridge assets.