As leading concrete repair contractors in the Chicago area, we are often asked, “Why does concrete crack in the first place?” Our clients want to know how to prevent their driveways, sidewalks, patios, and garage floors from needing future concrete crack repairs.
The bad news is that all concrete will crack, no matter what you do. The good news is that cracking can be controlled and mitigated by a talented installation team or concrete lifting contractor, and that concrete resurfacing is an affordable solution for repair.
In today’s post, our concrete repair experts at B&B Concrete Lifting will go over the three basic types of concrete cracking, and how to avoid each. We’re dedicated to delivering results that help keep your concrete level and in great shape for years to come, so no matter why it originally cracked, you can contact us for expert concrete repair today!
Concrete is made of a mixture of water, cement, and aggregates like rock, sand, and gravel. Any material with water content will shrink as it dries out and the water evaporates. This is why concrete will inevitably crack, no matter what you do, and this is also why you may see some cracking almost immediately — within 12 hours of pouring. The average 4-inch slab of concrete will shrink about a quarter inch for every 100 square feet of surface.
Since shrinkage cracking is inevitable, concrete contractors prepare for it with something called control joints. These are designed cuts in the surface that go down through at least half of the slab (like the grooves you see at regular intervals on sidewalks).
Control joints, also called relief joints, are intended to create weak points in the concrete to control where cracking will occur. As it dries out and shrinks, the concrete will crack along the control joint to release pressure, preventing uncontrolled cracking elsewhere.
The risk of uncontrolled cracking during shrinkage is increased by:
- Poor water ratio — too much water in the concrete mixture makes it easier to pour, but it also makes it weaker and more likely to crack
- Weather conditions — extreme weather temperatures, rapid temperature fluctuations, and wind and rain can increase the risk of cracking
- Poorly spaced control joints
- Larger slab size
Structural cracking happens when pressure is unevenly built up in certain places in or under a structure. As buildings “settle” over time, their weight shifts slightly, and this shifting weight, along with soil erosion and additional compaction, can create fluctuating pressure points that put strain on concrete. Since concrete cannot flex, it will crack to relieve this pressure.
Structural cracking is most common in older buildings, and it can often pose a safety concern. When structural cracks create wide gaps or variations in the concrete’s height, they become tripping hazards and should be repaired promptly.
The only way to mitigate settlement cracking is to hire an excellent concrete contractor from the start. They can’t guarantee your concrete will never crack, but they can do everything in their power — including compacting the foundation soil properly, designing good control joints, and closely supervising the mixing, pouring, and curing processes — to minimize the risk.
Finally, one of the most frustrating types of concrete cracking is craze cracking. This type of crack is purely aesthetic — it poses no structural or safety issues. Sometimes called “alligator skin cracking” or “map cracking,” craze cracking looks like a cracked desert floor: fine, jagged veins across the surface that visually fragment the concrete into chunks.
Craze cracking happens when the concrete’s surface “skin” dries faster than the inside of the slab, and it’s usually evident within days of pouring. It’s more likely to occur in dry, hot, or windy conditions during slab placement. Concrete should not be poured in temperatures above 90 degrees Fahrenheit, as the heat will “flash cure” the mix.
Contact B&B Concrete Lifting for Concrete Repair Today
No matter why your concrete is cracked, you can rely on our concrete repair experts at B&B Concrete Lifting to get it back in shape today. We have years of experience helping people throughout the St. Charles and Fox Valley areas with commercial and residential projects like:
- Concrete driveway repair and resurfacing
- Sidewalk repair
- Garage floor repair
- Concrete deck and patio repair
- Concrete step repair
- Mudjacking and concrete lifting
If you need concrete floor repair, then contact us today for industry-leading services and long-lasting results! B&B Concrete Lifting is ready to give your concrete a fresh start.