Types Of Cracks In Concrete Slabs | All You Need To Know

Types Of Cracks In Concrete Slabs

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Are you the type to start panicking the minute you see a crack on concrete slabs? 

Well, good news for you – it’s not always that serious! In fact, not all concrete cracks result in structural damage. This is because most of these concrete cracks appear during construction or may be caused due to external factors. 

Yet we understand if looking for the best concrete crack filler is the first thing you do on spotting even a hairline gap. You may even go to the extent of learning how to fix a crack in a foundation wall or how to repair cracks in concrete

But before you get started, you need to learn about the different types of cracks in concrete. This way, you’ll be able to fix the issue more effectively and prevent more cracks and damage in the future. 

So, without further ado, let’s get into the deets… 

Different Types Of Concrete Cracks

Plant for the production of reinforced concrete slabs and foundation blocks for large-panel construction. Panels for the construction of reinforced concrete structures. Industrial enterprise. Different Types Of Concrete Cracks.

1. Plastic Shrinkage Cracks

Before hardening, concrete is said to be in “plastic” condition when it is full of water. Gradually, the water fully evaporates, thereby leaving huge holes on the concrete surface. As you may have guessed, these holes weaken the structure of the concrete, making it more prone to damage. Hence, these are known as plastic shrinkage concrete cracks. 

Notably, these types of cracks are very common and can emerge on walls and slabs. However, you must watch out for these cracks on the corners and center of the concrete slab affixed with plumbing fixtures.

2. Horizontal Concrete Cracks

Horizontal cracks are usually spotted around areas of high tensile strength, such as column faces, column junctions, and beams. They are usually caused by improperly reinforced concrete, incorrect placement of installed reinforcement, uniaxial bending, insufficient moment resistance capacity, etc.

Note that horizontal concrete cracks call for immediate attention as they can degrade structural integrity.

3. Diagonal Cracks

If you’ve got a reinforced concrete slab, diagonal cracks are bound to appear along the concrete column face. These types of cracks may be caused due to inefficient load-carrying abilities, weak cross-section, insufficient reinforcement steel, and more. But unlike some minor cracks on concrete surfaces, diagonal cracks must be repaired immediately to prevent any damage to the entire structure.

4. Expansion Concrete Cracks

The nature of concrete is such that it expands when heated, further pushing anything that gets in its way. And as concrete does not bend or flex, such expansion causes it to break, creating concrete cracks.

Interestingly, expansion joints are used as points of isolation against static objects. This reduces the chances of concrete cracking in the future. 

Moreover, expansion joints are used as shock absorbers as they are made of a compressible material like rubber, timber, or asphalt.

5. Splitting Cracks

If you spot short vertical cracks of varying widths along the concrete slab, they are most likely caused by a lack of load-bearing capacity, improper cross-section and steel reinforcing. You must also ensure that the concrete used is of top-notch quality to avoid splitting cracks in the future.

6. Settling Concrete Cracks

If the ground beneath the concrete slab settles and creates a void, you may notice settling cracks. For instance, when a large tree is chopped/uprooted and the hole is not refilled with soil, settling cracks can occur on the concrete surface. Another suitable example is when a utility company digs around for its services and leaves the surface bare. 

7. Concrete Cracks As a Result of Premature Drying

When the concrete dries too soon, you may notice two types of surface cracks – crazing cracks and crusting cracks.  

Crazing cracks look like spider webs and form when the concrete slab loses moisture soon after application. While these surface cracks may be an eyesore, they do not pose any structural damage.

On the other hand, crusting cracks usually occur during the concrete stamping process. Again, this happens when the concrete surface dries up too quickly due to sunny or windy days. Plus, the stamp getting pressed on the concrete creates more texture and minute fissures. These types of cracks are also not a major concern, so you need not stress about them. 

8. Concrete Fissures Induced By Slab Overload

We are well aware of concrete’s strength and durability. But like every other material out there, it has its fair share of flaws. As such, excessive weight can cause cracks in concrete columns. 

Although overloading of the actual concrete slab is highly unlikely in residential areas, heavy rain or snow can make things worse. This is because the excess weight presses down the concrete slab into the moist earth, thereby resulting in cracks. 

9. Corrosion Cracks

These cracks start off at the same width but end up getting larger with time. You’ll mostly find such corrosion cracks on concrete column reinforcements. 

Like most of the concrete cracks described above, these are also caused by improper bonding between concrete and steel bars. Another reason could be reinforcement corrosion. 

Heaving Concrete Cracks

Sometimes it’s not just the carelessness or mistakes during construction but also natural factors that cause concrete cracks. For instance, the ground rises a few inches while freezing and goes back to its original size when thawed. Hence, if the concrete slab does not move with the ground, it will end up cracking.

The same thing happens when tree roots, both large and small, shift and shatter the surface if they’re too close to the slab. So, you must keep these factors in mind while laying a concrete slab. 

How To Repair Narrow Concrete Cracks

You get a wide variety of options for repairing narrow cracks – all you need is a caulking gun for the process. Not to forget, many concrete fixing products are available in bottles with a convenient applicator tip.

In case of hairline cracks, you can use a vinyl concrete patching compound and smooth out the surface with a trowel or putty knife. The smoothening process is especially important because the concrete caulk tends to peel off after a few months. 

Also, note that sometimes narrow cracks can be deep enough to extend throughout the width of the concrete column. Thus, we recommend starting off by using a foam backer rod to stuff the crack and hold the concrete crack filler. 

In case you’re wondering about the size of the back rod, let us tell you that they are available in a wide variety of diameters. Just ensure that you pick one which is slightly larger than the width of the concrete crack, and you’re good to go.

Finally, you can screw in the backer rod with a screwdriver and then fill the crack with the concrete crack filler. 

How To Repair Wide Concrete Cracks

Before learning how to repair cracks in concrete, it is important to understand the main aim, i.e., to create an inverted “V” with the sides of the crack. Doing so will allow the repair material to get absorbed into the crack and create a mechanical bond along with the chemical bond. Now, let’s check out the steps involved: 

Step 1

Use a masonry chisel and hammer to widen the crack and chisel it. Make sure that you remove any loose material from the old concrete with the help of a wire brush. 

Step 2

You can even use a pressure washer or a garden hose to spray the crack with high pressure water and remove debris. Then take a brush or wet/dry shop vacuum to remove the water as well. Remember that it’s okay to leave the surface damp/wet, but there shouldn’t be any pools of water. 

Step 3

Now follow the manufacturer’s instructions and prepare the concrete patching compound. Scoop the mixture into the concrete crack, ensuring no air pockets are left. Also, use some of the compound on the surrounding concrete surface for better adhesion. 

Step 4

Use a trowel to smoothen the surface and level it along the surrounding concrete. You can even use a brush to create patterns or textures. 

Step 5

Leave the concrete compound to dry and cure. Here, you must check the manufacturer’s instructions and follow them to the T! 

Finally, if required, you can paint or seal the entire surface. 

Types Of Cracks In Concrete Slabs Frequently Asked Questions ?

How to choose the best concrete crack filler?

Concrete crack fillers are available in various forms; namely, sealants/caulks, quick-setting cement, hydraulic cement, patching compounds, epoxy, and concrete resurfacer. Depending on the width of the crack, your level of expertise, time at hand, prevailing weather conditions, etc., you can choose a suitable sealer for cracks in concrete. 

How to remove concrete crack filler?

You can use an angle grinder and scrape off the concrete crack filler from the desired surface. 

How to prevent cracks in concrete surfaces?

While concrete crack fillers can fix present cracks, they cannot guarantee any prevention from future damage. Hence, it is important to maintain the structural integrity of concrete columns. 

You can do so by adding sealants every few years to protect the surface from top-layer damage. A good-quality sealant can harden the surface and prevent scratches, oil stains, and more. 

Other than that, you can invest in routine power-washing, wherein all the dirt and grime are removed with high-pressure water. If you have already used concrete crack fillers, then rest assured that the surface will remain protected with no water seeping into small gaps. 

Types Of Cracks In Concrete Slabs Final Words.

Types Of Cracks In Concrete Slabs Final Words

Though not all types of concrete cracks spell trouble, it is always wise to repair them early on to prevent any possible damage to the entire structure. And while it is difficult to find the root cause of the crack, possible reinforcement corrosion, improper jointing, and inefficient load-carrying abilities are usually the ones to blame. 

Hence, good concrete finishing techniques and proper site preparation must be ensured to avoid structural concern in the future. 

Ann Hutchinson

Ann Hutchinson

Ann Hutchinson is the heart of the team, senior editor and our Head of Product Reviews which means she sets the testing parameters of each group review ensuring that tests resemble everyday use.

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