It’s a given that a concrete slab will become cracked over time. This is particularly true at cold joints, where two concrete slabs meet that were poured at different times.
If the concrete slab is outdoors, such as a driveway, cracks need to be sealed properly. This keeps water from seeping under the slab and eroding the soil, which can cause the concrete to settle.
To seal a cracked concrete slab:
- Remove any debris or loose concrete in the crack using a screwdriver, followed by a wire brush.
- Use a broom or leaf blower to clean out the crack.
- Fill the crack with concrete repair caulk, such as Polyurethane Concrete Crack Sealant from Quikrete.
- On cracks that are wider than 1/4” push foam backer rod into the crack with a screwdriver, so it’s 1/2” below the surface, then fill the crack with concrete repair caulk.
Watch this video to find out more.
- Repairing Cracks in a Driveway (video)
- How to Seal Expansion Joints in a Concrete Driveway (video)
- Repair Cracks and Resurface a Concrete Driveway (video/article)
- Flexible Concrete and Brick Crack Repair Caulking (video)
Concrete driveways require a lot less maintenance. You want to keep them nice and clean, but more importantly, you want to be sure you fill up any cracks you might have, especially a crack like this.
Now, this is called a cold joint, where this slab and this slab were poured at different times. And no matter what you do, it’s going to result in cracked concrete.
Now, here’s what’s important about sealing that crack up, is that if you allow rain to get in this crack, sooner or later it’s going to affect the integrity of the soil below it. This will start settling and cracking, I’ve seen it a hundred times.
Here’s all you have to do is take a screwdriver, and just kind of scratch away at any debris you may have in the crack. Then, a wire brush to really clean it up really well. And then use a whisk broom. Or, I’ll tell you what, a leaf blower works really well on this as well.
Then, the important thing is a concrete repair caulk, this particular one is a self-leveling. And on a crack like this, you basically are just filling it in, and making it nice and flat.
Now, that works well on cracked concrete like this. But if you have a crack that’s a little larger — for some reason on this side, it’s a little larger than on that side — you’ll need this extra step.
It’s a backer rod, and you use this anytime you’re caulking anything on the outside of your house that’s larger than say a quarter-inch or three-eighths. And here, I’m going to put it down in the crack, like that. Screwdriver, push it down about a half-inch. Then, I’ll caulk right over it, just like I did the smaller crack.