Your driveway is peeling, and it may not be only the salt

Flaking is easy to misread, and a patch that ignores the cause can peel again. This guide helps you name what you see and ask better questions before you pay for a second patch.

Contractors and homeowners use different words for the same damage. Use your own words first, then match them to the trade term so you can follow a quote.

• Thin peeling in patches that merge: scaling, the flaking or peeling of the finished surface.
• A fine web of tiny cracks: crazing, usually shallow and often cosmetic.
• Thin skins lifting off in layers: delamination, where the surface separates from the concrete below.
• Small cone-shaped holes: popouts, where a stone near the surface has broken away.

Take close photos of each, with a coin in the frame for scale. Send them with your first message to any contractor. A person who can see the damage can say more than one who only hears "it is flaking."

NOAA's 1991 to 2020 normals for the airport put roughly 84 days a year where the temperature swings above and below freezing. A slab that sits wet gets frozen and thawed over and over.

Add salt. Road crews spread it, and cars carry it onto your property. It reaches slabs you never salted yourself, including the apron and the garage floor.

You cannot change the weather. You can change what goes into the slab and how it is treated in its first winter. That is where a repair either lasts or fails, so spend your attention there.

Concrete that will freeze while wet needs air entrainment. Air-entrained concrete is full of microscopic air cells, billions per cubic foot. When water in the slab freezes, it has tiny chambers to expand into, which relieves the pressure.

The idea has local roots. The published history says state highway engineers in New York hit on the fix in the early 1930s while chasing a cure for salt scaling on new pavement.

The amount depends on the stone in the mix. For the freezing classes that include salt exposure, ACI 318 targets 6.0 percent total air for the three-quarter inch and one inch aggregate sizes that flatwork commonly uses. NRMCA recommends the same 6 percent for slabs with those sizes. New York's residential code sets a band of 5 to 7 percent air for exposed steps and garage slabs.

Ask your contractor to name the air content in the written scope, and ask what the supplier's ticket will show on the day. If the answer is "standard mix," ask again.

ACI 318 groups concrete by exposure, and its most severe class, F3, is freezing and thawing with water and de-icing chemicals. A wet driveway that gets salted fits that description.

The trade group NRMCA says to skip de-icing chemicals in the first winter, then use them sparingly. For traction on new concrete, it suggests clean sand instead. It adds that ammonium sulfate, ammonium nitrate and magnesium salts are harsh on a slab and should stay off.

Check the bag before you buy. If you are repairing in the fall, tell your contractor you plan to use sand on the new work, and ask what they would put in writing about it.

Cars matter too. NRMCA suggests rinsing off the salt that cars drop on driveways and garage slabs when the weather allows. Water that pools and stays salty makes scaling more likely.

Here is the part many people miss. NRMCA notes that concrete can peel even where freeze-thaw plays no part. It blames troweling too early with steel, finishing too much, or finishing while bleed water still sits on top.

If your slab began to peel in its first season, finishing may be the cause, and the mix may be fine. If it peeled after many winters, wear and exposure are more likely.

Ask yourself when it started. Tell the contractor, who can then ask the right questions about when the slab was poured and how it was finished. Skipping that step is how a patch ends up repeating the original mistake.

You will hear a strength figure in quotes, and the sources do not agree. NRMCA, working with ACI 332, the residential concrete code, suggests 4,000 psi for exterior slabs that stay wet and see de-icers. ACI 318 sets 4,500 psi for plain concrete in its F3 class, but that figure is written for structural concrete, and NRMCA points home slabs to ACI 332. The state's residential code sets 3,500 psi for garage floors and exposed steps where weathering is severe.

Do not treat one of those as the only right answer. Ask the contractor which figure the written scope uses and why. A contractor who can explain the choice has thought about your slab, and one who cannot may be copying a stock line.

Strength alone does not fix scaling. Air, water content, finishing and curing all work together, so ask about each of them.

NRMCA calls light scaling a cosmetic matter that may need no repair at all. It also says that a slab with heavy, progressing scaling may not be repairable.

Light to moderate scaling can be repaired, but the new surface is only as strong as the old surface it bonds to. Weak concrete has to be removed first, and the repair material will look different from the original.

That is a useful test of an honest quote. If a contractor says a thin topping will solve the problem, ask what they are bonding it to. If the slab beneath is crumbling, a coating over it has nothing sound to grip.

Sometimes replacement is the better answer, and sometimes a repair is enough. Ask the contractor to explain both, in writing, with the reasons.

1. What do you think caused the flaking: the mix, the finishing, the salt, drainage, or a mix of them?
2. What air content will the new concrete have, and where is it written?
3. Which month will you pour, and what is your plan for the first winter?
4. How will the unsound surface be removed before the repair goes on?
5. What should I use for traction and ice this winter on the new work?

Bring that list to every quote and compare the answers side by side. We are not the contractor, and the concrete work is theirs. We can help you work out what to ask and introduce you to an independent local contractor to quote it. Tell us what your slab looks like.