Does salt hurt asphalt? Asphalt driveway winter care

Does salt damage asphalt?

Not much, directly. Asphalt is bound by a petroleum-based binder that rock salt does not dissolve the way it can attack concrete paste. The indirect effect matters more: salt melts snow into water, and that water runs into cracks and refreezes when the temperature drops. Every melt-and-freeze cycle pushes a crack a little wider.

So salt is not the enemy. Water in the wrong place is.

The real enemy: water in cracks

Water expands roughly 9 percent when it freezes. In a hairline crack, that expansion pries the pavement apart. Repeat it through dozens of freeze-thaw cycles in a Michigan winter and a hairline crack becomes a chunk that breaks loose, which becomes a pothole by March.

That is why the most important winter care for asphalt happens in the fall.

Fall prep

1. Fill cracks with a crack filler rated for asphalt. Anything wider than a hairline is worth filling.
2. Sealcoat if it is due, in warm, dry weather, following the product's temperature guidance. Sealcoat needs warmth to cure, so do not wait until November.
3. Fix drainage. Extend downspouts that empty onto the driveway, and make sure water can run off the edges instead of pooling.
4. Mark the edges. Asphalt edges, especially on older drives, are often thin and crumbly. See driveway markers.

Plowing asphalt

• Edges are the weak point. A blade that rides off the edge of an older asphalt drive can break it up. Markers help the crew stay on the pavement.
• New asphalt stays softer for a while after it is laid. If yours was paved this year, tell your contractor so the crew is careful turning and setting the blade.
• Skid shoes set slightly high avoid scraping the surface, especially over patched areas.

Snow piles and meltwater

Pile snow where it will drain away from the driveway, not at the top of a slope or against the garage. A pile that melts across the pavement every afternoon feeds cracks with water every night. It also creates black ice at the bottom of the drive.

Using salt on asphalt

Use it the way you would anywhere: shovel or plow first, then treat what is left, and use less than the bag suggests. Below about 15°F rock salt stops doing much at all; calcium chloride works in deeper cold, and traction sand works at any temperature.

Spring checklist

1. Sweep up sand and grit.
2. Look for new or widened cracks and fill them once it is warm enough.
3. Patch small potholes before they spread.
4. Plan sealcoating for warm weather if the surface looks gray and dry.