Monitoring Steel Corrosion Challenges

1
Monitoring Steel CorrosionChallenges

• Direct inspection of the rebar or corrosion
  coupons, sensors is almost impossible as these
  are embedded in concrete.
• Retrofitting of corrosion probes/sensors is
  difficult.
• Concrete is actually a complex composite
  material, whose structure and properties tend to
  change with time. It does not "behave" like
  simple aqueous corrosion systems.
• Cracks in the concrete may represent a major
  factor in the severity of corrosion damage.
• Chloride induced rebar corrosion tends to be of
  the localized variety.
• Corrosion damage is typically manifested over
  many years of exposure.

2
Corrosion Monitoring Methods

• ER probes
• Extracted core samples
• Chloride concentration profiles or carbonation
  depths
• Soundness
• Permeability of concrete
• Visual inspection.

3
Maximum Load Monitor

• The TRIP steel sensor unit (in foreground) is
  attached to a bridge, and the maximum strain
  experienced by the bridge is permanently recorded
  by a change in the magnetic character of the
  steel. The sensor is read by the portable
  instrumentation unit shown in the background.
• TRIP steel is a special steel with a special
  chemical formulation, and it undergoes a
  permanent change in crystal structure in
  proportion to peak strain. It changes from a
  non-magnetic to a magnetic steel. The change can
  be easily measured.