Are hairline cracks in concrete normal?
When you see a crack in your concrete slab or wall, your first guess is usually that something has gone wrong, but that’s not always the case. Indeed, cracks in concrete are very common, some are even unavoidable.
Why do hairline cracks appear in concrete?
Hairline cracks often occur due to shrinkage, either from drying or heat. These types of cracks are more difficult to control. Because they usually occur near the surface, reinforcement does not help prevent them. The best prevention is to use a good mix design that has a low tendency to shrink.
How to repair hairline cracks in a concrete slab?
You can repair hairline cracks in concrete with a Portland cement and water-based grout. Add just enough water to the cement to form a thick paste. Dampen the old concrete along the hairline crack with water for several hours before adding grout.
When should I be worried about cracks in concrete?
Generally, cracks in your floor are nothing to worry about. The only time you might worry is if the cracks start to shift vertically, suggesting there is settlement.
Can I just paint over the hairline cracks?
For deeper hairline cracks, you can use putty to fill the cracks before applying a fresh coat of paint to the affected area. However, if a large area has been affected, you will need to scrape off the paint, then sand the entire area to even out the edges before applying a new coat of paint.
Can you prevent concrete from cracking?
To prevent plastic shrinkage, the key is to keep the concrete surface moist by covering it with burlap, polythene sheets, or plastic. This is especially important in extreme weather conditions such as high winds, hot temperatures, or direct sunlight.
How big is a crack in a concrete slab?
– Larry B. Hairline cracks in a concrete slab are rarely a cause for concern. They can be controlled, but not eliminated. A crack in a slab of 1/8 inch or less is usually a normal shrinkage crack and not a cause for concern.
Why do I have hairline cracks in my concrete wall?
If the cracks appear shortly after a concrete foundation is poured, the concrete may have been mixed improperly or poured too quickly. In poured concrete foundations, hairline cracks frequently appear in the center of the walls because the corners of the walls have greater stability.
Is it normal for a concrete floor to crack?
Indeed, cracks in concrete are very common, some are even unavoidable. The American Concrete Institute addresses the issue of cracking in concrete in its American Concrete Institute Handbook, ACI 302. 1-40: “Even with the best floor designs and proper construction, it is unrealistic to expect to floors without cracks or bends.
Where do plastic shrinkage cracks in concrete come from?
While plastic shrinkage cracks can occur anywhere in a slab or wall, they almost always occur at re-entrant corners (corners that poke into the slab) or with circular objects in the middle of a slab ( pipes, plumbing fixtures, drains and manholes).