Advances In Monitoring

The Embedded Corrosion Instrument – ECi-2 – monitors the corrosive environment in steel-reinforced concrete over three crucial periods in the life of a structure: in construction, during the curing of concrete, and on a long-term basis during use of the structure.

The builders, engineers, and owners of a structure can use ECi-2 to monitor chloride ion concentration trend, temperature, and resistivity, helping identify construction errors at an early stage. One such error may be the use of saline or contaminated water in the mixing of concrete.
ECi-2 can be used to monitor temperature and moisture content, helping ensure maximum strength of the concrete.
The owners and managers of the structure can use ECi-2 to monitor five key factors in corrosion – linear polarization resistance, open circuit potential, resistivity, choloride ion concentration trend, and temperature.

Traditionally, the owners and managers of a structure have monitored corrosion through visual inspection or the use of analog probes. Unfortunately, however, these techniques are subject to severe limitations. Visual inspection is costly, labor-intensive, and fails to reveal deterioration within a structure.

eciBridgeAnalog probes, by contrast, can be embedded within concrete. To gather data from these devices, however, inspectors must tour a structure and insert a reader into each probe site. Like visual inspection, this process is expensive and labor-intensive, and it generates data only at the time of each visit. To address this issue, engineers may wire the probes to send their readings to a datalogger. Because these transmissions are analog, however, they’re highly vulnerable to electro-magnetic interference. The greater the distance between the probe and the datalogger, the more their connecting wire functions as an antenna, suffering electro-magnetic interference from power lines, radio waves, and cell phones. Also very importantly, each analog probe has historically measured only one or two parameters of the corrosive environment.

Virginia Technologies has designed the ECi-2 to solve these problems. Embedded in a structure during construction, the ECi-2 monitors the corrosive environment within steel-reinforced concrete. Because its sensors are integrated with on-board processing electronics, the ECi-2 carries its signals only a short distance – approximately one inch – before analog-to-digital conversion. This maximizes the signal-to-noise ratio, prevents electro-magnetic interference, and facilitates more accurate, repeatable measurements.

iStock_000031172560_SmallFrom each ECi-2, those measurements are automatically transmitted to a datalogger. This eliminates the need for inspectors to take manual readings. That, in turn, minimizes the costs of inspection and makes it economically feasible to gather corrosion data continuously, rather than every few months. In this way, the ECi-2 ensures that warning signals are received at the earliest possible date – when the costs of remediation are lowest.

 

The ECi-2 also transmits its readings to the datalogger via digital signals, rather than analog wave-forms. This makes it possible to place each ECi-2 up to 200 feet from the nearest datalogger – rather than 30 feet, as in the case of analog probes. In this way, the ECi-2 facilitates coverage of a far larger area by each datalogger, minimizing the cost of supporting electronics. With the flexibility offered by this greater distance, structure managers are also able to place dataloggers in more favorable, sheltered locations. Furthermore, because ECi-2 readings are digital, maintenance engineers can download them remotely, and integrate them into computerized structure management systems.

 

Finally, and perhaps most importantly, the ECi-2 monitors not one or two, but five key factors in corrosion – linear polarization resistance, open circuit potential, resistivity, choloride ion concentration trend, and temperature. This provides more comprehensive data than prior generations of sensors. It also reveals correlations among the causes and signs of corrosion, yielding a fuller, more certain picture of the threat.

 

In all of these ways, the ECi-2 represents a substantial advance in the technology of corrosion monitoring for steel-reinforced concrete structures.