What is spalling?
Spalling is the chipping, flaking or breaking away of small pieces of material from the surface of concrete, brick or masonry. It appears as small craters, pits or flakes on the surface and can indicate quality problems or damage to the structure.
What causes spalling?
Spalling can have several causes:
- Frost damage — water in the material expands when it freezes, pushing fragments off the surface
- Pop-outs — reactive particles in the aggregate swell and push a cone-shaped piece of concrete away
- Corrosion — rusting reinforcement expands and forces the concrete cover off (cover spalling)
- Fire — extreme heat causes explosive spalling as trapped moisture turns to steam
- Lime blows — unslaked lime particles in bricks expand and cause small spalls
Applications
- Quality control — spalling in bricks is tested according to standards. Bricks with excessive lime inclusions are rejected
- Concrete repair — spalled concrete is repaired with patching mortar after the cause has been identified
- Prevention — adequate concrete cover, air-entraining agents and frost-resistant bricks prevent spalling
- Inspection — in existing structures, spalling is a signal to investigate the reinforcement and concrete quality
Related terms
- Concrete
- Frost damage
- Concrete corrosion
- Brickwork
- Concrete cover
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