Why are our crew members dragging a chain across a concrete surface and striking it with a hammer? We’re checking for delamination, which may be hidden and often can be “heard” before it is seen.
Typically, when metal strikes solid concrete, it produces a clear, ringing sound. But if a dull, drum-like thud or loud clack is heard, there are likely hollow areas in the layers of concrete. Dragging a chain across concrete surfaces and listening for a change in tone helps us find extensive damage that has occurred below the surface due to water intrusion, which can damage the rebar and cause delamination. Striking the concrete with a hammer helps further pinpoint these voids.
Delamination occurs when thin layers of the slab, typically 1/8 to 1/4 inch thick, separate from the base concrete of a finished slab. This problem often occurs if finishing operations start prematurely and close or seal the surface before excess air and water can bleed out of newly poured concrete, creating subsurface voids where air or water was trapped. These voids create weakened zones right below the surface that can eventually detach under use, especially if your concrete is exposed to heavy traffic or wheel loads.
It is important to address signs of delamination early to avoid extensive repairs such as removing and resurfacing the top layers of concrete. Schedule now for an early spring appointment to have your concrete inspected for delamination and other hidden, or not-so-hidden, signs of damage so that you can take preventive action before they become costly repairs.