How to Prevent Concrete Spalling & Deicer Salt Damage in Winter

After spending thousands of dollars on a new concrete driveway or walkway, the last thing you want is for the surface to start flaking, scaling, and pitting. This peeling effect is called spalling, and it is one of the most common concrete issues in cold climates.

Spalling is often blamed on a bad concrete batch, but the real culprit is a combination of water, freeze-thaw cycles, and chemical deicing salts. It is closely related to why concrete cracks. Here is why concrete spalls and how you can prevent it.

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1. How Freeze-Thaw Cycles Damage Concrete

Concrete is highly porous, behaving like a hard sponge. It contains millions of microscopic capillaries. When it rains or snow melts, water is absorbed into the surface of the concrete.

When the temperature drops below 32°F, that water freezes. Water expands by 9% when it turns to ice. When confined inside the pores of the concrete, this expansion creates immense internal hydrostatic pressure (up to 100,000 PSI).

As this cycle repeats dozens of times throughout the winter, the pressure ruptures the cement bonds near the surface, causing it to flake off in thin sheets.

Rain/Snow Melt ──► Water Absorbed ──► Temperature Drops ──► Water Expands 9% ──► Hydrostatic Pressure ──► Surface Spalls/Flakes

2. The Danger of Deicing Salts

Deicing chemicals (such as sodium chloride, calcium chloride, and magnesium chloride) do not chemically attack the concrete itself. Instead, they accelerate physical damage.

Salts lower the freezing point of water. This increases the number of freeze-thaw cycles the concrete undergoes. Instead of freezing and thawing once a day, the concrete may go through 3 to 4 freeze-thaw cycles in a single day as the sun rises and sets, multiplying the internal expansion stress.

Furthermore, salts are hygroscopic, meaning they pull and hold water from the air. This increases the amount of water trapped inside the concrete capillaries, leaving less room for the ice to expand.

[!WARNING] Never use chemical deicers on concrete that is less than one year old. Young concrete has not reached its full compressive strength and contains high levels of moisture, making it highly vulnerable to scaling.

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3. How to Prevent Concrete Spalling

Use the Right Mix Specs

If you are pouring new concrete in a freeze-thaw climate, specify an air-entrained concrete mix of at least 4,000 PSI (see 3,000 vs. 4,000 PSI concrete). Air entrainment introduces billions of microscopic air bubbles into the mix. These bubbles act as expansion chambers. When the water freezes, it moves into the bubbles rather than rupturing the cement paste.

Apply a Penetrating Sealer

For existing concrete, the best protection is a silane-siloxane penetrating sealer. Unlike topical sealers (like acrylics) which sit on top of the concrete and wear away, penetrating sealers chemically bond with the concrete pores, creating a hydrophobic water-repellent barrier. Water bead up on the surface and cannot penetrate the slab, preventing freeze-thaw damage entirely. (For the full trade-off, see acrylic vs. penetrating sealers.)

Safe Alternatives to Salt

To gain traction on icy driveways without causing spalling:

• Use clean sand or kitty litter. They provide grip without chemical side effects.
• Avoid ammonium sulfate and ammonium nitrate fertilizers, which will chemically dissolve concrete.
• Shovel snow promptly to prevent it from melting and soaking into the concrete.