Your first thought when you see a break in your concrete slab or wall is that something has gone wrong–but this isn’t always the case. Concrete cracks are very normal, and some are unavoidable. Plus, you need to have this info if you’re looking to build a concreting company Sydney relies on.
American Concrete Institute touches on the issue of cracking concrete in their American Concrete Institute manual, ACI 302. 1-40:
“Even with the best floor designs and proper construction, it is unrealistic to expect crack-free and curl-free floors. Consequently, every owner should be advised by both the designer and contractor that it is normal to expect some amount of cracking and curling on every project, and that such occurrences do not necessarily reflect adversely on either the adequacy of the floor’s design or the quality of its construction”
We explain 6 of the most common types of concrete cracks below.
Plastic shrinkage concrete cracks
Concrete is full of water because it is still in its plastic state (before hardening). When the water evaporates from the slab, it leaves wide gaps between the solid particles. The concrete becomes softer and more vulnerable to breaking as a result of these empty spaces. This method of cracking is known as “plastic shrinkage cracking” and occurs commonly.
Plastic shrinkage cracks can appear anywhere in a slab or wall, but they almost often occur at reentrant corners (corners that point into the slab) or in the center of a slab with circular pieces (pipes, plumbing fixtures, drains, and manholes). Since concrete cannot shrink around a corner, tension can cause it to crack at the corner’s point.
Plastic shrinkage cracks are usually very small and hardly noticeable. Although plastic shrinkage cracks are almost invisible, it’s necessary to note that they don’t just occur on the surface; they run the length of the slab.
Concrete shrinkage may be exacerbated by an overly damp combination. Although water is an important component of any concrete mix, there is such a thing as too much of it. The slab will shrink faster if there is too much water in the mix than if the right amount of water is used. Plastic shrinkage fractures are also caused by hot temperatures.
To resist shrinkage splitting, control joints may be inserted into the slab. When the concrete slab becomes thinner, the joints will free up.
Expansion concrete cracks
Concrete expands in the same way as a bubble does when it is heated. Concrete stretches and drives against everything that gets in the way (a brick wall or adjacent slab for example). When neither can flex, the expanding force is strong enough to allow concrete to break.
Expansion joints serve as a separating (or isolation) point between two static surfaces. Expansion joints, which are often made of a compressible material such as cement, rubber, or timber, must serve as shock absorbers to ease the tension that concrete expansion places on it to resist cracking.
Heaving concrete cracks
When the earth freezes, it can rise several inches before thawing and returning to its original position. The freezing and thawing cycle causes significant ground displacement, which contributes to concrete cracking. The slab will break if it is not free to pass with the earth.
On a slab, large tree roots will have the same impact. The rising roots of a tree planted too close to a slab will raise and break the concrete. When laying a slab, keep this in mind.
Settling concrete cracks
Land settling under a concrete slab, on the other hand, may cause cracking.
Settling cracks are most common where a hole in the ground under the concrete surface is formed. Consider what happens when a big tree is cut down nearby and the roots tend to decompose, or where a service firm digs a trench with their lines, tubing, and other equipment and doesn’t compress the soil when filling it–these are examples of situations where settling cracks are likely to occur.
Concrete cracks caused by overloading the slab
Concrete is a very solid construction material, but it has limitations. Putting so much weight on top of a concrete slab will cause it to break. When you hear that a concrete mix has a PSI of 2000, 3000, 4000, or 5000+, it refers to the pounds per square inch used to smash the concrete slab.
Overloading of the concrete slab itself is uncommon in suburban concrete slabs. Excessive overload on the ground under the slab is more likely to occur.
Excessive weight on the slab after a hard rain or snowmelt, when the ground below is soft and muddy, will push the concrete down and cause cracks.
Concrete cracks caused by premature drying
There are two kinds of cracks that are often caused by premature drying.
Ground cracks that resemble spider webs or broken glass are known as crazing cracks. Crazing cracks occur as the surface of a concrete slab loses moisture too easily. Crazing cracks, although unsightly, are not a structural problem.
Crusting cracks are most often seen during the concrete stamping period, which adds color and pattern to concrete surfaces. The top of the concrete surface will become crusty on sunny or windy days when the top of the slab dries out faster than the bottom. When a stamp is embedded, it tears the soil apart at the stamped joints, causing minor fractures along the “stones’ outer edges. While crusting cracks are unsightly, they are not a structural problem to be concerned with.
It’s not really easy to figure out what triggered a single crack. Site planning, a proper blend, and good concrete coating techniques can both help to reduce the presence of cracks and provide a more aesthetically appealing concrete project.
With what we’ve discussed, you should have a basic idea of the different types of concrete cracks. Feel free to go over this article again for a more solid grasp. This will also allow you to know how to know a quality mixed concrete. Plus, you’ll be able to detect if a concrete should be replaced or not. As we stated earlier, this info is important, especially if you’re looking to start a concreting company Sydney relies on.