Navigation

Do deicers really cause spalling?

by Deb Ballheim
(Littleton, Colorado)

Recent spalling on the driveway

Q. I am finding all kinds of conflicting information about whether deicers can cause spalling on concrete driveways. What is the real answer? We have a house that is only three years old and the driveway seems to be crumbling away in one winter. I have attached a picture - this concrete was perfectly smooth before this winter. I included a yard stick in the picture for reference. Some places have deteriorated right down to the aggregate.

A. Deicing salts do cause damage to concrete, but usually starts as small pits. The reason is salt creates more freeze and thaw cycles which is concrete's worst enemy. But looking at your photo, I don't believe your problem is salt. It looks to me like something happened during finishing. Your concrete is experiencing what's called scaling which results from a weak bond between the surface and the rest of the concrete. When the paste on the surface hardens at a different rate than the concrete under it, it prevents proper bonding therefore creating a weak surface.
So what would cause the different hardening rates? Adding water to the surface during finishing is the most common culprit. Maybe the concrete set up too fast and water was added to aid finishing. Or maybe the concrete was rained on. Unfortunately, if that's what happened the problem will worsen and the only fix is to tear it out and repour it.