19 June 2001
Table 5-5 Sampling Equipment, Measurements and Ratings for Concrete
Special Sampling Equipment
Measurement, Ratings or Samplings
Half-cell potential measurements
Location and size of damaged area
Depth of chips, cracks, spalls, etc.
Concrete-core rotary drill
Drilled concrete cores for laboratory analysis
The inspector should be alert for any change in appearance of the
concrete surface and any change in the sound from the hammer:
Erosion of the surface material or by cracking on the surface are
signs of chemical attack.
Erosion of surface material is a sign of freeze-thaw deterioration.
Use a hammer or gad (sharp pointed tool) to chip or probe the surface
Corrosion of the reinforcement can be detected from rust stains on the
surface. More advanced stages of corrosion is indicated by cracks that run
parallel to the steel reinforcing bars. At times, corrosion is hidden from view, but
will be indicated by a hollow sound from the hammer. This can occur on heavily
reinforced slabs, such as pier decks, where the reinforcement has corroded
enough to delaminate a layer of concrete at the level of the reinforcing mat.