In new slabs, finishing delaminations form when the surface is densified before trapped air and bleed water escape, leaving a thin layer that sounds hollow and later breaks loose. In bridge decks and garages, delamination is a horizontal crack at the rebar level driven by corrosion, located by dragging a chain or tapping with a hammer and listening for a drummy sound. Both end in spalling if left alone.
Chain drag found delamination over about a third of the deck, mostly over the top mat where the cover's thin.
Also heard as
- delam
- delams
- hollow spot
Related terms
Blistering
Hollow bumps that form on a troweled slab when air or bleed water gets trapped under a sealed surface.
Spalling
Chunks or flakes breaking away from a concrete surface or edge, often from corroding rebar beneath.
Burn
To steel-trowel a slab again and again at high blade pitch until it turns hard, dark and glossy.
Cover
The depth of concrete protecting the outermost bar, measured from the bar to the nearest face.
Laitance
The soft, chalky skin of fines that bleed water leaves on top of concrete, too weak to bond to.
Same word, different worlds
Separation of a coating from its substrate or of one coating layer from another.
Printed Circuit BoardsSeparation between layers of a board's laminate or between laminate and copper, usually from heat or moisture.
NonwovensSeparation of the layers of a laminate or multilayer nonwoven, such as an SMS or a film composite.