Concrete Repair Guide: Cracks, Spalling, Resurfacing

Last updated: October 27, 2026

Concrete repair fixes a damaged slab without replacing it, and it starts with knowing which of 4 problems you have: cracking, spalling, delamination, or settlement. From ten feet away they can look alike. But each one has its own cause and its own fix. Most advice skips that and jumps straight to a product, and that’s backwards. The material almost never decides if a repair holds. The diagnosis and the prep do.

We’re based in Prague, OK, and a fair share of the calls we take end with us telling someone their slab is fine. So this page also sorts the flaws worth money from the ones that are just concrete being concrete. It covers cast-in-place concrete, the slabs, driveways, and walks poured right on site.

Does every concrete crack need repair?

No. Hairline cracks under about 1/8 inch are normal in any slab. They’re shrinkage cracks. Concrete shrinks as it cures, and it has to give somewhere. Control joints are there to pick where. ACI 224.1R, the American Concrete Institute’s guide to cracks, treats fine cracks like these as normal, not as a failure. You can clean and seal one to keep water out, or leave it alone.

The cracks worth money are wide, growing, higher on one side, or letting water down into the soil. A crack wider than about 1/4 inch means something moved. So does a crack with one side sitting higher than the other. What moved once can move again. Fill the gap without finding out why, and the repair fails twice.

How do you tell what you’re looking at?

Delamination and spalling get mixed up all the time, and the test for them is free. Tap the top 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. And there is one. The top layer has split off from the slab below but hasn’t broken loose yet. Spalling is the same failure one step later, once the top has flaked or chipped away. It often starts at joints and edges, where de-icing salt collects.

Scaling is something else. It’s the thin top skin of cement paste wearing off from freeze-thaw and de-icing salt. A lab test called ASTM C672 grades how well a mix holds up to it. A slab that scaled badly in three winters wasn’t unlucky. It was finished too early, finished with water worked into the top, or mixed short on air. That’s entrained air, the tiny bubbles that give freezing water room to swell.

For cracks, three things split harmless from serious: width, movement, and offset, which means one side sits higher. Draw a mark across the crack and check it over a season. A crack that opens in January and closes in July is still moving. Seal a moving crack with rigid epoxy, and you’ve just moved the failure a half inch to one side. Now the epoxy is stronger than the concrete next to it, so the concrete is the part that breaks.

Which repair method fixes each problem?

Crack routing and sealing. We widen the crack into a clean channel with a saw or a grinder, then fill it. A crack that moves gets a flexible polyurethane sealant. One that doesn’t gets rigid epoxy, per ACI 546 guidance. This is the cheapest work on the page, and it’s priced by the linear foot of crack.

Epoxy injection is the fix for a structural crack. It does more than bridge the break. It bonds both sides back together, so the slab acts like one piece again. It’s the right call only after an engineer confirms the cause is fixed. Inject a crack that’s still moving, and all you bought is an expensive line in the concrete.

Partial-depth patching fixes most spalling. We saw-cut a clean edge around the damage. Then we chip out everything weak, down to sound, rough concrete that matches an ICRI 310.2 profile. The patch is a polymer-modified mortar, or an ASTM C928 rapid-set mix that can take traffic in a few hours. When the damage runs wider than a few patches, our concrete repair and resurfacing work pairs patching with an overlay in one pass.

Resurfacing and overlay is for a slab that’s sound underneath but done on top: worn, patched, stained, tired. A concrete overlay from 1/4 inch to 1 inch thick bonds a new top to the old one. It can take color or a decorative finish at the same time. What it can’t do is fix something moving underneath. Put an overlay over a moving structural crack, and that crack shows right back through, on schedule.

Slab lifting fixes settlement without a repour. That covers most of the sunken driveways, walks, and garage slabs we see. Polyurethane foam goes in through holes the size of a dime. It cures in about 15 minutes, so you usually get the slab back the same day. Mudjacking pumps a slurry of cement and soil through bigger holes. Its material costs less. Either one usually beats tear-out and repour by 30 to 50 percent. Our concrete leveling crews do both. The concrete leveling guide puts foam, mudjacking, and a new slab side by side.

Full removal and replacement comes last for a reason. It costs the most and keeps you off the slab the longest. And it’s the only choice here that throws away concrete with twenty good years left in it.

Why prep decides whether a repair lasts

A well-bonded repair lasts 10 to 20 years, and often as long as the rest of the slab. The prep decides that, not the mortar. A repair bonds to whatever it sits on. Put a patch over dusty, delaminated, or loose concrete, and it’s resting on a layer that already failed once. It doesn’t matter what the bag cost.

ICRI 310.2 is the repair industry’s chart of surface textures, from a light broom texture up to rough, bare stone. Each repair material calls for its own texture. Then we soak the old concrete so it’s damp with no standing water, a state called saturated-surface-dry, before the patch goes on. We check the bond with a pull-off test, ASTM C1583. You glue a small metal puck to a cored spot and pull until something breaks. A good result breaks in the old concrete, not at the repair line. If it lets go clean at the seam, the repair was never stuck on, whatever the invoice said.

Prepped wrong, the same mortar from the same crew can pop loose in its first freeze-thaw cycle.

Replacement starts winning at about a third of the slab

Past that line, chasing patches costs about what a new slab would, and at the end you own a patched slab instead of a new one. If the slab is broken into many pieces, or it sank too far for lifting to bring it back to grade safely, the choice is already made. But most slabs people think need replacing don’t. A spalled garage floor gets patched and resurfaced. A sunken patio gets lifted. A cracked driveway gets routed, filled, and sealed.

1. Crack routing and sealing, priced by the linear foot.
2. Slab lifting, usually 30 to 50 percent under tear-out and repour.
3. Partial-depth patching and resurfacing in the middle. Patching cost rides mostly on how much weak concrete has to come out.
4. Full removal and replacement at the top, with the longest downtime.

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

The same bond line behind a finished floor

Every method on this page comes down to one bond line. That same line decides if a Slab Boss polished floor or a RESA resin floor is still there in fifteen years. Prep the surface, check the bond, then place the material. A crew that takes that seriously on a decorative floor takes it seriously on a driveway patch. A crew that doesn’t, doesn’t. Is your fixed slab headed for a finished floor? The concrete overlay guide shows how an old slab gets there. The overlay service page lists what the work includes.

Send photos before you send money.