Why is the Surface of My Concrete Flaking Off?

Why is the Surface of My Concrete Flaking Off? Understanding Spalling

When the surface of your concrete starts flaking, chipping, or breaking away, you're dealing with spalling—a serious problem that gets worse if not addressed. Understanding what causes it and how to fix it prevents further damage and restores your concrete.

What is Spalling?

Spalling is the deterioration and breaking away of the concrete surface. It starts as small chips and flakes, then progresses to larger areas peeling away, exposing the aggregate underneath.

Primary Causes of Spalling

Freeze-Thaw Damage

This is the most common cause in cold climates:

How Freeze-Thaw Damage Works

1. Water enters concrete pores and cracks
2. Water freezes and expands (water expands 9% when frozen)
3. Expansion creates pressure that breaks the concrete
4. Repeated cycles cause progressive damage
5. Surface flakes away, exposing more concrete to water

Why It Happens

• Concrete wasn't properly sealed (allows water entry)
• Existing cracks let water penetrate
• Poor drainage allows water to pool
• Repeated freeze-thaw cycles over multiple winters

Salt on Fresh Concrete

Using de-icing salt on concrete less than 1 year old causes rapid spalling:

Why Salt is Especially Damaging to New Concrete

• New concrete is more porous and absorbs salt water easily
• Salt lowers the freezing point, creating more freeze-thaw cycles
• Chemical reaction with fresh concrete accelerates deterioration
• Damage appears quickly and is severe

How Salt Causes Spalling

1. Salt solution penetrates concrete pores
2. Creates concentrated freeze-thaw cycles
3. Repeated expansion and contraction breaks surface
4. Chemical reaction with concrete compounds accelerates damage

Other Causes

Over-Finishing

• Bringing too much water and fine particles to surface during finishing
• Creates weak surface layer
• This weak layer flakes away over time

Poor Curing

• Inadequate curing allows surface to dry too quickly
• Creates weak, porous surface
• More susceptible to damage

Rebar Corrosion

• Rusting rebar expands, pushing concrete away
• More common in older concrete
• Causes delamination and spalling

How to Identify Spalling

Signs of spalling include:

• Small chips and flakes coming off the surface
• Pitting and surface deterioration
• Exposed aggregate (you can see the stones/pebbles)
• Progressive worsening over time
• Worse in areas exposed to water or salt

How to Prevent Spalling

Proper Sealing

• Seal concrete to prevent water entry
• Reseal every 2-3 years (sealing costs vary by project size and sealer type)
• Use quality sealers appropriate for your climate

Avoid Salt on New Concrete

• Never use salt on concrete less than 1 year old
• Use sand or kitty litter for traction instead
• After first year, if you must use salt, use calcium chloride or magnesium chloride (less damaging than rock salt)

Fix Cracks Promptly

• Seal cracks to prevent water entry
• Use flexible polyurethane sealant
• Address cracks before winter freeze

Ensure Proper Drainage

• Water should drain away from concrete
• Fix drainage issues promptly
• Prevent water from pooling on or around concrete

How to Repair Spalling

For Minor Spalling

1. Clean the area thoroughly
2. Apply concrete patching compound
3. Smooth to match surrounding surface
4. Allow to cure properly
5. Seal the entire surface

For Extensive Spalling

• May require resurfacing
• Apply thin layer of concrete resurfacer
• Or consider full replacement if damage is severe
• Consult a professional for evaluation

The Bottom Line

Spalling (surface flaking) is caused by freeze-thaw damage or using salt on fresh concrete. Water enters concrete, freezes and expands, breaking the surface. Salt accelerates this process, especially on new concrete. Prevent spalling by sealing properly, avoiding salt on new concrete, fixing cracks, and ensuring good drainage. Repair depends on severity—minor spalling can be patched, extensive damage may require resurfacing or replacement.

Once spalling starts, it progresses if not addressed. Fix the underlying cause (water entry, salt use) and repair the damage promptly to prevent further deterioration.

Need help with spalling? Contact Local Concrete Contractor. We can evaluate the damage, identify the cause, and provide repairs that prevent further deterioration.