BUILDING INSPECTION, MAINTENANCE
AND FACILITY MANAGEMENT
Corrosion Monitoring of Rebars Inside Concrete Structures
How might we accurately inspect rebars inside concrete structures for corrosion, using a non-destructive testing approach?
Challenge Statement Owners
Background and Current Practice
Corrosion monitoring is important in Singapore due to high humidity levels and proximity to saltwater bodies. Linear Polarisation Resistance and Open Circuit Potential measurements are the common tests for corrosion monitoring of reinforcing bars (“rebars”) inside concrete structures. Both tests require hacking of the concrete cover surrounding the rebars, so that contact can be made with the rebar to complete a circuit. These concrete covers usually have a thickness of 20mm but can have a thickness of up to 50mm for critical structures. Some structures have exposed wires connected to rebars to ease the process of measurement testing, but this cannot be replicated throughout the entire structure.
The current practice is time consuming and hard to execute, especially when workers have limited access to the site (for example, in the scenario where tunnels and the site are already in operation). The hacking of concrete cover damages the concrete structures and could hasten corrosion rates when the rebar is exposed to air and moisture.
Opportunities and Key Challenges
An inspection or monitoring technology that allows for a non-destructive testing approach towards both the concrete and rebar would improve the corrosion monitoring process by eliminating the need to hack off the concrete cover.
We are open to different measurement techniques, such as impedance or electrical pulse. One way to monitor for corrosion is to study the chlorine penetration and pH level in the concrete layer as well as the condition of the passive film layer surrounding the rebar.
Concrete usually has a pH level of 12 and can decrease when chlorine penetrates the concrete and destroys the passive film layer surrounding the rebar.
The solution needs to be battery powered and portable to be feasible for field applications.
We are also interested in solutions that can help us determine the rate of corrosion and lifespan of a concrete structure.
The solution assists the inspection and/or monitoring process of the state of rebar or concrete to accurately identify if corrosion has taken place. Repair actions can then be taken to prevent further damage.
Such a solution would help to eliminate the time and manpower needed to remove the concrete cover, while maintaining or lowering the total cost of corrosion monitoring.