Spalling
Surface deterioration where concrete flakes, chips, or breaks away in fragments
Spalling is surface deterioration where concrete flakes, chips, or breaks away in fragments, typically starting as small patches that grow larger over time. It's one of the most common visible failures in concrete, especially in freeze-thaw climates.
Why It Matters
Spalling isn't just cosmetic—it exposes aggregate and reinforcement to moisture and chemicals, accelerating deeper deterioration. Left unchecked, spalling can progress from surface damage to structural failure. Driveways with spalling lose load-bearing capacity and create tripping hazards.
Prevention is far cheaper than repair. Proper concrete mix design (including air entrainment in cold climates), adequate curing, and sealing can prevent most spalling. Once spalling starts, it typically worsens quickly unless repaired and sealed.
Technical Details
Common causes of spalling:
Freeze-thaw damage: The most common cause. Water enters concrete, freezes (expanding 9%), and breaks surface layers. Requires both water penetration and freezing temperatures. Air-entrained concrete with proper spacing of microscopic air bubbles provides freeze-thaw resistance.
Corrosion of reinforcement: When rebar or wire mesh corrodes, rust occupies more volume than steel, creating internal pressure that pops off concrete. Requires inadequate concrete cover over reinforcement (less than 2 inches) and moisture/chloride penetration.
Scaling from deicers: Calcium chloride and other deicing salts can react with concrete paste, creating surface scaling (a form of shallow spalling). Potassium acetate or sand are safer alternatives.
Poor finishing: Overworking the surface brings excess water and paste to the top, creating a weak layer prone to spalling.
Related Terms
- Scaling - Similar but shallower surface loss
- Freeze-Thaw - Cyclic freezing and thawing that causes spalling
- Delamination - Separation of concrete surface layers
Learn More
- Identify freeze-thaw spalling vs. other surface damage →
- How to Repair Concrete Cracks - Fixing damaged concrete
- How to Seal Concrete - Preventing moisture-related problems
- Concrete Calculator - Plan your concrete project