Short answer
Concrete scales when water in its surface freezes, expands and breaks off the top layer, and de-icing salts make that damage worse. Air-entrained concrete, a well-drained base, proper finishing and curing, sealing and careful de-icing choices are the main defences. None of them make concrete immune.
Last updated October 2, 2026
How freeze-thaw damage happens
Concrete is porous. Water soaks into the surface and, when temperatures drop below freezing, that water turns to ice and expands. Repeated freezing and thawing over a winter can flake off the thin top layer, which is called scaling, or break away larger pieces, which is called spalling. Southern Ontario winters with frequent freezing and thawing are exactly the conditions that cause it.
De-icing salts make the problem worse. Salt lowers the freezing point and draws more moisture into the surface, which increases the number and severity of freeze-thaw cycles at the surface. Concrete that is poorly finished, over-troweled, not cured or not air-entrained is especially vulnerable.
What helps concrete survive
| Protection | What it does | When it is decided |
|---|---|---|
| Air-entrained concrete | Tiny air bubbles give water room to expand when it freezes | At the time of ordering the mix |
| Exterior-grade strength and mix design | Denser, less permeable concrete resists water entry | At the time of ordering |
| Compacted base and drainage | Keeps water from sitting under or on the slab | Before the pour |
| Careful finishing | Avoiding overworking the surface or adding water keeps the top layer strong | During the pour |
| Proper curing | Lets concrete gain strength and reduces surface cracking | After the pour |
| Sealing | Reduces water and salt absorption | After curing, then periodically |
| De-icer choice and amount | Using less, and the right type, reduces chemical stress | Every winter |
For exterior flatwork exposed to freezing and de-icing salts, the Canadian standard CSA A23.1 sets minimum strength and air content requirements under exposure class C-2. In general industry terms, that means air-entrained concrete of about 32 MPa. Ask your contractor to confirm the mix in writing.
De-icers and traction: what to do and avoid
- Avoid salt in the first winter on new concrete where you can. Young concrete is more vulnerable. Many contractors suggest sand for traction instead.
- Use as little de-icer as you can. Shovel first, then apply a thin amount where needed.
- Avoid products with ammonium nitrate or ammonium sulphate, which can chemically attack concrete.
- Do not let salty slush sit. Clear meltwater and slush off the surface when possible.
- Keep vehicles from dripping salty slush onto the driveway where practical.
- Rinse the surface in spring to remove residual salt.
We are not recommending specific products. Read manufacturer guidance and ask your contractor what they advise for your concrete and sealer.
Sealing: what to know
Sealers fall into two broad groups. Penetrating sealers soak into the surface to reduce water and salt absorption without forming a visible film. Film-forming sealers sit on top and can change the look of the surface. Either needs reapplying over time. Ask your contractor which product they use, whether it is suitable for freeze-thaw and de-icer exposure and how often it should be renewed. Sealers can make some surfaces slippery when wet.
Timing matters. Concrete should cure before it is sealed, and sealing before the first winter is common advice.
Repair or replace
Light scaling on an otherwise sound slab can sometimes be repaired or resurfaced. Widespread scaling, deep spalling or settlement usually points to replacement. See concrete repair and resurfacing and concrete driveways for what each route involves.
Frequently asked questions
Why is my concrete driveway flaking?
The most common cause is freeze-thaw damage to the surface, made worse by de-icing salts and by concrete that was not air-entrained, was finished too wet or was not sealed.
Does road salt damage concrete?
Salt does not simply dissolve concrete, but it increases the damage from freezing and thawing at the surface, which leads to scaling.
What should I use instead of salt on a new driveway?
Many contractors suggest sand for traction in the first winter. Ask your contractor for their advice.
Can scaled concrete be fixed?
Sometimes, with a resurfacing overlay if the slab is sound. Widespread damage usually means replacement.
How often should concrete be sealed?
It depends on the product and exposure. Ask your contractor or the sealer manufacturer for the right interval.
Is air-entrained concrete required in Ontario?
It is the standard recommendation for exterior concrete exposed to freezing and de-icers. Check what your contractor is specifying.