Spalling
Concrete breaking away from a structural member, pushed off from behind by corrosion products forming on the reinforcement. Rust occupies several times the volume of the steel it came from, and that expansion splits the cover.
On an actual building
Spalling means the member is already losing section, and it is a falling-material hazard. It is a structural signal rather than a finish defect, and it warrants diagnostic testing rather than patching.
What we most often have to correct
That the damage is what you can see. The corrosion always extends beyond the spalled area, which is why repairs cut back further than the visible failure.
Terms that come up alongside this one
- Incipient Anode Effect
New corrosion that begins immediately around a concrete repair patch.
- Chloride Attack
Corrosion of reinforcement driven by chloride ions penetrating the concrete, typically from sea air, sea spray or brackish groundwater.
- Carbonation
The slow reaction of atmospheric carbon dioxide with the alkaline compounds in concrete, which lowers its pH.
More deterioration terms
Spalling — questions we get asked
What does spalling mean in waterproofing?
Concrete breaking away from a structural member, pushed off from behind by corrosion products forming on the reinforcement. Rust occupies several times the volume of the steel it came from, and that expansion splits the cover.
Why does spalling matter on a real project?
Spalling means the member is already losing section, and it is a falling-material hazard. It is a structural signal rather than a finish defect, and it warrants diagnostic testing rather than patching.
What do people commonly get wrong about spalling?
That the damage is what you can see. The corrosion always extends beyond the spalled area, which is why repairs cut back further than the visible failure.
Have a building showing this?
If a term on this page describes something you are looking at, a site inspection will tell you how far it has gone and what it needs. It costs nothing.
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