How Freeze-Thaw Cycles Damage Concrete (And What You Can Do About It)

Concrete driveways, sidewalks, and patios are built to last — but in Ontario's climate, they face one of the most destructive forces in construction: the freeze-thaw cycle. If you've ever noticed flaking, pitting, or surface crumbling on your concrete after winter, this is almost certainly why. Here's how it works and what you can do about it.

What Is a Freeze-Thaw Cycle?

A freeze-thaw cycle happens when water enters the tiny pores and cracks in concrete, then freezes and expands. Water expands by about 9% when it freezes. That expansion puts enormous pressure on the surrounding material. When the ice melts, water seeps deeper into the crack before freezing again. Each cycle pushes the crack a little further open.

In London, Ontario, we can experience dozens of freeze-thaw cycles in a single winter — especially during those stretches of mild days followed by cold nights that are so common in January and February. This repeated expansion and contraction is what causes the surface of concrete to flake away, a process called spalling.

Why New Concrete Is Especially Vulnerable

Concrete that was poured in the last year or two is more susceptible to freeze-thaw damage. It hasn't fully cured to its maximum hardness, and it hasn't been sealed yet. If your driveway or sidewalk is relatively new, it's especially important to apply a quality concrete sealer before the cold months arrive.

The Role of Road Salt

Road salt accelerates freeze-thaw damage. Salt lowers the freezing point of water, which actually increases the number of freeze-thaw cycles the concrete experiences. It also draws moisture into the concrete and can react chemically with the concrete paste, weakening the surface over time. If you're using salt on your concrete driveway or walkway, switching to a sand-based traction aid during the winter months can make a real difference over time.

What You Can See (And What You Should Do)

Common signs of freeze-thaw damage include:

• Surface flaking or peeling (spalling)
• Fine surface cracks forming a web-like pattern (crazing)
• Larger cracks that seem to grow wider every spring
• Chunks of concrete breaking off at the edges

If you're seeing any of these, don't ignore them. Small cracks can be filled and sealed. Larger spalling or deep cracking may require a partial resurface or full section replacement depending on the severity.

Prevention Is Cheaper Than Repair

Sealing your concrete before winter is the single most effective way to prevent freeze-thaw damage. A good penetrating sealer fills the pores in the surface and dramatically reduces how much water can work its way in. It should be reapplied every few years, especially after a harsh winter.

For existing damage, catch it early. A crack that's a few millimetres wide today can become a much bigger problem by next spring if water gets in and the freeze-thaw cycle does its work.

Lawns & Lanes handles concrete sealing and repair throughout the London area. To get an assessment of your driveway or sidewalk, call us at 226.234.6541 or visit lawnsandlanes.ca.