Concrete Delamination Survey

Birmingham City Laboratories

Delamination or Tapping surveys

Delaminations are not usually visible on the concrete surface, but wet stains or nearby spalling concrete may indicate areas where delamination is likely. Sounding is a simple and effective method to identify and locate delamination below the concrete surface. Striking the surface of a concrete section with an hammer or steel bar to detect planes of delamination. On horizontal surfaces such as bridge or car park decks a metal rod can be used to sound the surface or alternatively various types of chain drag can be used. The chain drag technique is believed to be less accurate than simple hammer or rod soundings. ASTM D 4580 recommends the sounding procedures to detect delaminations in pavements and slabs.

A change in sound near the area of the delamination indicates the presence of delamination. The surface over a defective area emits a hollow or drum sound. A sound area that is not delaminated emits a ringing noise.

Concrete delamination

Some force may be necessary to sound concrete for delamination where the cover to the steel is greater than about 40–50mm. Although a club hammer will locate laminations accurately at this depth, beyond 100mm sounding concrete can be ineffective in picking up deep laminations.

The survey may require the removal or coring though some of the delaminated sections to determine the depth of the delamination and the condition of the reinforcement steel.