When embedded steel rusts, the corrosion products occupy several times the volume of the original metal and push off the cover concrete in slabs, columns and balconies. Spalls also come from freeze-thaw damage, impact at joint edges, fire and trapped moisture. Repair means chipping back to sound concrete and behind the corroded bar, cleaning or replacing the steel and patching.
Garage level two has spalling at every column base, salt's been running down to that rebar for years.
Also heard as
- spall
- spalls
Related terms
Cover
The depth of concrete protecting the outermost bar, measured from the bar to the nearest face.
Delamination
A surface layer that has split away from the concrete below it, found by the hollow sound it makes when tapped.
Green bar
Epoxy-coated rebar, named for its usual green coating, used where salt and chlorides threaten corrosion.
Scaling
Thin patches of surface mortar coming off a slab, usually after freeze-thaw cycles with deicing salt.
Same word, different worlds
Flaking of large chunks from a bearing race or gear tooth after fatigue cracks below the surface link up.
Thermal SprayFlakes or chunks of coating breaking away from the surface, typically under thermal cycling or impact.
Refractories & Furnace LiningsCracking off of pieces or layers from the hot face of a refractory lining.
Gear EngineeringLarge, irregular flakes broken out of a tooth surface, usually where pits have grown and joined.
Sealants & WaterproofingConcrete, brick or stone breaking off in flakes or chunks at the surface.