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 by striking the surface of a concrete section with a hammer or steel bar to detect planes of delamination.
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. Some force may be necessary to sound concrete for delamination where the cover to the steel is greater than about 40–50mm. A hammer will locate laminations accurately at this depth, sounding concrete beyond 100mm 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.