6 Types of Concrete Cracks

Kwik Concrete Contractor Tulsa OK Pros is often contacted by people who are interested in other concrete companies’ work. Most concrete cracks within the first year after placement. This is the most common question we get.

Does Concrete Cracks?

Concrete shrinks on average by 1/16th of an inch for every 10 feet when it is curing. Although this may seem like a small number, shrinkage cracking is a common mistake in concrete. Concrete can fail much faster when it is under tension.

Tulsa is a colder climate and we must deal with a freeze/thaw cycle. Concrete slabs on grade are subject to extreme weather cycles, such as sidewalks, patios and driveways that change with the seasons. Each winter, the ground freezes and forces it to rise. The sun thaws ground when it comes out. However, this does not always happen evenly. A portion of the concrete slab may melt and drop in the sun, while the rest will remain in shadow and be stuck to the ground. Concrete can crack due to this stress.

Below are 6 common concrete crack types.

1. Concrete cracks shrinking plastic
Concrete is water-filled when it is still in its original plastic state, before hardening. The slab will eventually lose water, leaving behind large gaps between the concrete particles. This makes concrete more susceptible to cracking and weakens it. This is known as “plastic shrinkage cracking” and it happens quite often.

Plastic shrinkage cracks may occur anywhere on a slab or wall. However, they are most common at reentrant corners (corners which point into the slab) and with circular objects (pipes or plumbing fixtures, drains or manholes) in the middle. Concrete cannot shrink around corners, so stress can cause concrete to crack at the corner.

Plastic shrinkage cracks can be very small in width and are barely visible. Although they are almost invisible, plastic shrinkage cracks can be seen throughout the entire slab.

Concrete shrinkage can be caused by a wet mix. Water is an important ingredient in any concrete mix. However, too much water can cause concrete to shrink. The slab will shrink if it contains too much water. Plastic shrinkage cracks can also be caused by hot weather.

To prevent shrinkage cracking, control joints can be integrated into the slab. As the concrete slab shrinks, the joints will expand.

2. Expansion concrete cracks
Concrete expands just like a balloon. Concrete expands and pushes against any object in its path (a brick wall, or an adjacent slab). Concrete can crack if it is unable to bend.

Expansion joints can be used to isolate static surfaces from one another. Expansion joints are typically made from a compressible material such as asphalt, rubber, lumber. They act as shock absorbers and relieve concrete of the stresses that expansion places on it.

3. Concrete cracks to be heaved
Ground can lift up to several inches when it freezes before thawing and returning to its original level. Concrete cracking can be caused by ground movement due to the freezing and thawing cycles. The slab will crack if it isn’t free from the ground.

Large tree roots can cause the same effect on a slab. The concrete surface can be cracked or lifted by roots growing too close to a slab if the tree is too close. This should be considered when you lay a slab.

4. Settling concrete cracks
Ground settling under a concrete slab can cause cracking.

When the ground below the concrete surface is disturbed, setting cracks are common. Consider removing a large tree from a nearby area and allowing the roots to decay. Or when utility companies dig a trench for their pipes, lines, or other utilities. Don’t compress the soil when you fill it with water. These are two examples of situations where cracks can occur.

5. Concrete cracks are caused by overloading the slab
Concrete is a strong building material but it has its limitations. Concrete slabs can crack if they are weighed down with too much weight. Concrete mix strength is the amount of weight required to crush a concrete slab. It can be stated as 2000, 3000 or 4000 PSI.

Residential concrete slabs are not prone to overload. Excess overload of the ground below the slab is much more common.

Concrete cracks can occur after heavy rain or snowmelt. This type of cracking is more common for homeowners who have large vehicles or dumpsters in their driveways.

6. Concrete cracks can be caused by excessive drying
Premature drying can cause cracks in two types.

Crazing cracks are extremely fine surface cracks that look like shattered glass or spider webs. Crazing cracks can develop when concrete slabs lose too much moisture. Although they are unsightly, crazing crackeds do not pose a structural problem.

Concrete stamping is a method of adding texture to concrete surfaces. Crusting cracks are most common during concrete stamping. The concrete surface’s top can become crusty on sunny days or when the slab top dries faster than the bottom. The stamp embedding causes the concrete surface to crack near the stamped joints. This can cause small cracks around the edges of the “stones”. Although they may not look very good, crusting cracks should not be considered a structural problem.

Sometimes it can be difficult to pinpoint the cause of a crack. Good site preparation, quality concrete mix and concrete finishing techniques can help minimize cracks and make concrete projects more pleasing.


How to stop concrete cracking

Nearly every concrete contractor conceals what is known as a “control joint”. To relieve concrete stress, this is a grove or cut in the concrete. These control joints should be placed at corners and with the proper spacing. Contractors who have been working in concrete for a while will be familiar with the best places to place these joints. This will ensure a pleasing appearance.

Kwik Concrete Contractor Tulsa OK Pros

R&M Concrete, Tulsa’s top concrete company, delivers quality work and excellent service on all concrete jobs.



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