Quick Answer
Concrete cracks from shrinkage as it cures, freeze-thaw cycling, and base settlement; control joints do not prevent cracks but direct them to planned lines.
All concrete moves, and some hairline cracking is normal as a slab cures. The goal is to control where it cracks, not to promise it never will — a distinction B.G. Concrete explains on every job rather than after the fact.
Concrete shrinkage cracks and control joints
As fresh concrete loses water it shrinks slightly, which is why control joints are cut on a planned layout to direct that shrinkage into straight, hidden lines. Cracks that follow the joints are doing exactly what they were designed to do.
Cosmetic cracks versus structural cracks
r/Concrete regulars note that many homeowners are told every crack is "normal" with no explanation. Thin surface cracks are usually cosmetic, while wide, offset, or actively widening cracks point to base settlement or missing reinforcement and deserve a closer look.
How Chicago freeze-thaw and road salt cause cracking
In the Chicago suburbs water enters small cracks, freezes, and pries them wider through 40-plus freeze-thaw cycles a winter, and de-icing salt accelerates the surface damage. Air-entrained concrete and a draining stone base are the defenses that keep cracking minor.
Related Questions
Are hairline cracks in concrete normal?
Yes — fine shrinkage cracks are normal; wide, uneven, or growing cracks are the ones worth evaluating. Read more about surface damage.
How long does concrete take to cure?
Concrete is walkable in 24 to 48 hours and reaches full strength at 28 days. Read more about cure time.
How long does a concrete driveway last?
A well-built concrete driveway lasts 30 to 40 years in the Chicago climate. Read more about driveway lifespan.
B.G. Concrete pours concrete across Wood Dale and the NW Chicago suburbs — see our new concrete care guide or call 630-595-1518 for a written figure.