By Bennett's Concrete and Excavation, Norwich, NY. Updated October 2026.
Three different problems
| Scaling | Spalling | Popouts | |
|---|---|---|---|
| What you see | The thin top layer flakes off in patches, exposing stone | Deeper chunks break loose, often along cracks, edges or over steel | Small cone-shaped pits, 1/4 inch to a few inches across |
| Main cause | Freeze-thaw, often with deicers, on a weak or non-air-entrained surface | Rusting steel near the surface, or impact and heavy loads at edges | Porous stone particles near the surface that crack when they freeze |
| When it shows | First few winters | Usually years later | Often the first year |
Sources: NRMCA guides on scaling, corrosion and aggregate popouts.
Scaling: the Central NY classic
NRMCA defines scaling as local flaking or peeling of the finished surface caused by repeated freezing and thawing. It starts as small patches that can merge. NRMCA grades it from light (no stone showing) to moderate (stone exposed, up to 3/8 inch of mortar lost) to severe.
NRMCA lists the causes:
- no entrained air, or too little near the surface
- low-strength concrete that lets water in
- heavy deicer use, especially on new concrete
- finishing with bleed water on the surface or overworking it
- poor curing
- placing exterior concrete late in the fall so it freezes while still saturated
Spalling: when steel rusts
Deeper damage often traces to reinforcement. NRMCA's corrosion guide explains that steel in concrete is protected by the concrete's high alkalinity, but chlorides from deicing salt break that protection down. Rust takes up two to four times the volume of the steel, which cracks and spalls the concrete above it. That's why NRMCA's cracking guide calls for at least 2 inches of concrete over steel in salted areas. Rust-colored stains along a crack are a warning sign.
Popouts: a stone problem
NRMCA describes popouts as small conical holes left when a porous stone particle near the surface absorbs water, freezes and breaks. Low-density chert is the most common culprit, and they usually show up in the first year. Most are cosmetic. NRMCA notes they can be patched by cleaning out the pit and filling it with a repair material, though matching the color is hard.
Why the first winter is the worst
Young concrete is the most vulnerable. It's still wet inside, still gaining strength, and its surface is the weakest it will ever be. NRMCA's cold-weather guide says concrete that will face freeze-thaw should reach about 3,500 psi before it does, and its scaling guide says not to use deicers on new concrete during its first winter. A driveway poured late in the fall may meet salt before it's ready. See new concrete winter care.
How to prevent scaling
NRMCA's recommendations for new exterior concrete:
- Air-entrained concrete, about 6 percent air for typical 3/4 to 1-inch stone. See air-entrained concrete.
- 4,000 psi for slabs that stay moist and get deicers.
- Slump of 3 to 5 inches, with no extra water at the truck.
- Finish after bleed water is gone, no steel trowel on exterior slabs. A broom finish is usually enough.
- Cure with a curing compound or wet burlap and plastic.
- No deicers the first winter, moderate use after.
- A breathable silane or siloxane sealer, ideally in late summer after a few dry days.
Deicers: what to avoid
NRMCA says never to use ammonium sulfate, ammonium nitrate or magnesium-based deicers on concrete. It describes plain rock salt and calcium chloride as acceptable in moderate amounts on concrete past its first winter, and recommends clean sand for traction and hosing off salt buildup when the weather allows. Our salt alternatives guide and snowplow guide cover winter care.
Repair or replace?
- Light scaling on sound concrete: clean it, let it dry and seal it to slow the damage.
- Popouts: patch the pits if they bother you.
- Widespread moderate or severe scaling: a resurfacing product can work on a sound slab, but if the concrete under the surface is weak, overlays often fail.
- Spalling over rusting steel, or slabs that are also cracked and sunken: usually a tear-out and replacement.
Our guide on whether to repair or replace a driveway walks through the decision. We do concrete sealing, including washing, degreasing and a salt-repellent sealer on aprons, and full removal and replacement when a slab is past saving.
