Why Your Concrete Driveway Is Cracking
Some cracking is normal
Concrete shrinks as it cures. Because the slab is held in place by friction with the ground and by its own weight, the shrinkage builds tension, and the concrete relieves that tension by cracking. That is why contractors cut control joints into a slab: they create planned weak lines where cracks form neatly. A few hairline cracks in a driveway that is several years old are common and mostly cosmetic. The trouble starts when cracks are wide, offset, or multiplying.
The five common causes
- Shrinkage and poor joints. Slabs poured without control joints, or with joints spaced too far apart, crack randomly. Adding water to the mix on site increases shrinkage.
- A weak base. If the soil under the slab was not compacted and there is no stone base, parts of the slab settle and the concrete cracks where it loses support.
- Expansive clay soil. Much of northeast Oklahoma sits on clay that swells in wet seasons and shrinks in dry spells. The movement lifts and drops sections of the driveway and breaks them.
- Freeze-thaw cycles. Water gets into small cracks, freezes, expands, and pries the crack wider. Non-air-entrained concrete and de-icing salts accelerate the damage, causing flaking and scaling of the surface.
- Heavy loads and tree roots. Trucks, trailers, and delivery vehicles can exceed what a 4-inch slab is designed to carry, and roots can push up a section of the slab.
Reading the crack
The shape of a crack tells you a lot. Thin hairline cracks that follow a joint are usually harmless. A crack wider than about one-quarter inch, or one where one side sits higher than the other, points to settlement or heaving. A web of small cracks across the surface, called crazing or map cracking, often comes from rapid surface drying or from finishing the concrete while it was wet. Corner cracks and edge chips come from loads near the edges or from lack of support.
What repair options exist
The right fix depends on the cause. Hairline and narrow cracks can be cleaned and sealed with a flexible concrete crack filler to keep water out. Wider cracks may need routing and filling with a sealant or a polymer repair product. Sunken slabs can sometimes be lifted by injecting material beneath them. When a slab is badly broken, settled in multiple places, or structurally unsound, replacement is the lasting answer, and the new slab should get a compacted base and proper joints so the problem does not repeat. See our driveway repair and driveway installation services.
When a crack means a bigger problem
Watch for cracks that grow over a season, cracks that let one section sit higher than its neighbor, and gaps where the slab pulls away from the garage or the street. Those point to movement under the concrete, such as washed-out soil from a downspout or a void left by settling. A raised edge is also a trip hazard, which makes it a safety issue for anyone walking the driveway. If you see a section that has dropped or heaved, have a contractor look at the cause before patching the surface, because filling a crack without fixing the movement only hides the problem for a season or two.
How to prevent new cracks
- Seal cracks early so water does not reach the base or freeze in them.
- Keep gutters and downspouts directing water away from the slab.
- Avoid de-icing salts. Use sand for traction instead.
- Keep heavy vehicles off a slab that was not built for them.
- Trim trees whose roots are heading under the driveway.
The American Concrete Institute and the Portland Cement Association both publish guidance on crack control. If you are thinking about replacing a slab, read how thick a concrete driveway should be first.
Cracked driveway in Bartlesville, OK? Bartlesville Concrete Pro provides a free written estimate on every project.
Call (539) 286-0805 Contact Us OnlineFrequently asked questions
Are cracks in a concrete driveway normal?
Some hairline cracking is normal as concrete cures and shrinks. Wide, uneven, or spreading cracks point to a base, soil, or load problem.
When should I repair a driveway crack?
Seal cracks as soon as you notice them so water cannot get in and freeze. Cracks wider than a quarter inch or with uneven edges should be evaluated.
Can cracked concrete be repaired instead of replaced?
Often yes. Narrow cracks can be sealed and some sunken slabs can be lifted. Badly broken or settled slabs usually need replacement.
Does clay soil crack concrete?
Yes. Expansive clay swells and shrinks with moisture and moves the slab, which is common in northeast Oklahoma.
Who repairs concrete driveways in Bartlesville, OK?
Bartlesville Concrete Pro repairs and replaces driveways. Call (539) 286-0805 for a free written estimate.