Concrete Repair Guide: Cracks, Spalling, Resurfacing

Last updated: August 20, 2026

Concrete repair covers four problems that look similar from ten feet away and behave nothing alike: cracking, spalling, delamination, and settlement. Each one has its own cause and its own fix. Most repair advice skips that part and jumps straight to a product, which is backwards. The material almost never decides whether a repair holds. The diagnosis and the prep do.

Our crews dispatch from Prague, OK, and a fair share of the calls we take end with us telling somebody their slab is fine. That’s the other half of this page: knowing which flaws are worth money and which ones are just concrete being concrete.

Does every concrete crack need repair?

No. Hairline shrinkage cracks under about 1/8 inch are normal in any slab. ACI 224.1R treats fine cracking as expected behavior rather than failure, because concrete shrinks as it cures and it has to give somewhere. Clean it and seal it to keep water out, or leave it alone. Both are legitimate answers.

The cracks worth money are wide, growing, offset in height across the gap, or passing water down into the soil below. Wider than about 1/4 inch, or with one side sitting higher than the other, means something moved. Something that moved once can move again, and filling the gap without finding out why is how a repair fails twice.

How to tell what you’re actually looking at

Two of those six get confused constantly, and the test is free. Tap the surface with a hammer or drag a chain across it. Sound concrete rings. Delaminated concrete sounds hollow and drummy, like there’s a void under it, because there is: the top layer separated from the slab below and hasn’t broken loose yet. Spalling is that same failure one step later, already flaked or chipped away.

Scaling is a different animal. It’s surface paste lost to freeze-thaw and de-icing salt, and how well a mix resists it gets graded under ASTM C672. A slab that scaled badly in three winters wasn’t unlucky. It got finished too early, finished with water worked into the surface, or batched short on entrained air.

For cracks, three things separate harmless from serious: width, movement, and offset. Mark across the crack and check it over a season. A crack that opens in January and closes in July is alive. Seal a moving crack with rigid epoxy and you’ve just moved the failure a half inch to one side, because now the epoxy is stronger than the concrete and the concrete is the part that loses.

Which repair method matches which problem

Crack routing and sealing. Widen the crack into a clean reservoir with a saw or a grinder, then fill it. Flexible polyurethane sealant for cracks that move, rigid epoxy for the ones that don’t, per ACI 546 guidance. This is the cheapest work on the page and it prices by the linear foot of crack.

Epoxy injection goes further on active structural cracks. It restores monolithic strength across the break instead of just bridging it, so the slab acts like one piece again. It’s the right call only after an engineer confirms the cause has been resolved. Inject a crack that’s still moving and all you bought was an expensive line in the concrete.

Partial-depth patching is the answer for most spalling. Saw-cut a clean perimeter around the damage, chip out everything unsound down to a roughened substrate matching an ICRI 310.2 profile, then place polymer-modified mortar or an ASTM C928 rapid-set material that opens to traffic in a few hours. When the surface damage runs wider than a few patches, our concrete repair and resurfacing work combines patching with an overlay in one pass.

Resurfacing and overlay is for a slab that’s structurally sound and cosmetically finished: worn, patched, stained, tired. A concrete overlay at 1/4 inch to 1 inch gives back a new wearing surface bonded to the old one, and it can take color or a decorative finish while it’s at it. What it can’t do is fix what’s moving underneath. An overlay over an active structural crack telegraphs that crack right back through, on schedule.

Slab lifting handles settlement without a repour, which covers most sunken driveways, walks, and garage slabs we see. Polyurethane foam injection goes through dime-sized holes, cures in about 15 minutes, and hands the slab back the same day. Mudjacking pumps a cement-and-soil slurry through larger holes at a lower material cost. Either one usually beats tear-out and repour by 30 to 50 percent. Our concrete leveling crews run both, and the concrete leveling guide puts foam, mudjacking, and replacement side by side.

Full removal and replacement sits last for a reason: highest cost, longest downtime, and it’s the only option on the list that throws away concrete with twenty good years still in it.

Why prep decides whether a repair lasts

The material gets the credit and the prep does the work. A repair bonds to whatever it’s placed on, so a patch over dusty, delaminated, or loose surface concrete is a patch resting on a layer that already failed once. It doesn’t matter what the bag cost.

ICRI 310.2 defines the surface profiles, from a light broom texture up to an aggressive exposed-aggregate finish, and the repair material dictates which profile it needs. Bond gets verified with a pull-off test under ASTM C1583: glue a dolly to a cored spot and pull it until something breaks. Here’s the part worth remembering. A passing result breaks in the parent concrete, not at the repair line. If it lets go clean at the interface, the repair was never attached, whatever the invoice said.

Prepped right, a bonded repair runs 10 to 20 years and often the remaining life of the slab. Prepped wrong, it can pop loose in the first freeze-thaw cycle. Same mortar. Same crew. Same day.

When does replacement start winning?

Roughly when the damaged area passes about a third of the slab. Past that line, chasing patches costs about what replacement costs, and at the end of it you own a repaired slab instead of a new one. If the slab is cracked into many pieces, or the surface is too far gone to keep, the math already settled itself.

Ranked by cost, cheapest first: crack routing and sealing, priced by the linear foot. Then slab lifting, typically 30 to 50 percent under tear-out and repour. Then partial-depth patching and resurfacing in the middle, with patching driven mostly by how much unsound concrete has to come out. Then full removal and replacement at the top, carrying the longest downtime with it.

Those are rankings, not quotes. Anyone who prices a repair without seeing the damage is pricing a guess.

The same discipline behind a finished floor

Every method on this page comes down to one bond line, and that’s the same thing that decides whether a Slab Boss polished floor or a RESA resin floor is still there in fifteen years. Prep the substrate, verify the bond, then place the material. A crew that takes that seriously on a decorative floor takes it seriously on a patch in a driveway, and a crew that doesn’t, doesn’t. For the path from repaired slab to finished floor, the concrete overlay guide walks the Pour-4-Polish route in more depth, and the overlay service page covers what the scope includes.

Send photos before you send money.