How To Fix Concrete Cracks

First off, what are cracks in concrete?

You may often see disintegration or gaps in your garages, slabs, and floors of concrete buildings. These gaps, called cracks in concrete, are often a sign of distress.

Sometimes the crack in concrete is inevitable and doesn’t mean something is wrong. Concrete provides mechanical strength and rigidity to a structure. The acceptable limit of a crack is 1/6 to ¼-inch-wide crack.

How do they occur?

These can happen in both fresh and plastic concrete due to some of the following reasons:

  • Changes in volume
  • Repeated loading on the concrete structure
  • Lack of control or relief joints that provide allowance to the structure.
  • Quick-drying or curing of concrete
  • Excess water in the concrete crack filler mixture.
  • Temperature changes or extreme temperatures lead to expansion and contraction.
  • Due to corrosion of reinforcement steel

Why should the cracks be fixed?

The cracks may lead to loss of structural integrity and reduction in the durability of the concrete structure. The life of the structure is shortened. It also looks unsightly and destroys the quality and beauty of the structure.

Types of cracks

The first step in fixing a crack is to diagnose its type. Analyzing the type of crack that has occurred helps us to know the best way to repair them. Depending upon the type of crack, a suitable method can be employed to repair them.


Plastic shrinkage cracks

As the water in the concrete begins to cure and lose water, the slab begins to shrink. This causes development of stress, that gradually becomes too great for the slab to withstand, and hence the slab cracks to relieve the tension.


Expansion cracks

Due to the increase in temperature in hotter climates, the concrete expands causing great stress on the slab, resulting in a crack.


Caused by heaving

Ground movements due to freeze or thaw cycles is the reason for such cracks. If the slab is constrained of movement, then it cracks.


Caused by setting

Due to the setting of a concrete slab to fill the void below it, you can find a crack.


Overloading of the slab

Placing excess weights on the slab beyond the load limits of the concrete often leads to cracking of the slab.


Crazing cracks due to premature drying

When the top of the concrete slab loses moisture too quickly, it can cause it to break down.

How To Fix Concrete Cracks - Some Methods

The next step is to adopt a suitable method to fix the concrete crack. Depending on the type of crack, a suitable method of repair is chosen from the following:


Epoxy injection

You can use this method for very narrow cracks as much as 0.05mm. You can carry this out by establishing inlet and outlet ports along the cracks and sealing the exposed surfaces. You should inject the epoxy under high pressure.


Routing and sealing

You can employ this method by expanding the cracks along its exposure and then filling and sealing it with a suitable joint sealant. You can use it for remedial repair conditions.


Crack repair by Stitching

It involves drilling holes on both sides of the crack and then grouting. You can use this method to reestablish tensile strength across the crack.


Additional reinforcement for crack repair

This is done by establishing reinforcement bars and holding them in place with epoxy resins.


Drilling and plugging method

Drill through the length of the crack and grout it to form a key, ideal when repairing vertical cracks in retaining walls.


Gravity filling method

After blasting the concrete surface to clean, you can use low viscosity monomers to fill the cracks by gravity. Some of the monomers that you can use are polyurethane and high molecular weight methacrylate.


Grouting method of crack repair

Portland cement ground is used to fill wide cracks. Though this cannot bond the crack, it is effective in preventing water leakage.


Overlay and surface treatments of cracks

Fine surface cracks that cannot move further can be treated by this method. You can do this by sealing the surface cracks by low solid and low viscosity resin-based systems.

Here is a Do-It-Yourself procedure to fix simple cracks concrete you can find at your garages and slabs.

You would require the following tools to carry out the procedure:

  • Broomstick
  • Cold chisel
  • Trowel
  • Hammer
  • Vacuum cleaner
  • A pair of gloves
  • A pair of safety glasses

Also, you would require the following materials:

  • Concrete patch material
  • Sealant

Here is the procedure as you should follow:

  • 1Wear the pair of gloves and safety glasses before setting down to work.
  • Clean the floor to make it free of dust, oil, and grease. Use grease cleaner as it will make the filler bond with the cement.
  • Clean using a cold chisel and a hammer to get rid of any large pieces. Place the hammer over the crack and pound it with the chisel holding it at a suitable angle. This is called ‘keying’ and it is done to make the crack bigger at the deep end than at the surface. It helps bond the patch material with the old crack.
  • After keying is carried out, clean the dust and debris using a whisk broom. Then, use a vacuum to make it a hundred percent dust-free.
  • Cut off the nozzle of the bottle and begin to fill. If you are using the patch concrete mix, then fill it according to the directions given in the user manual.
  • Use the trowel to fill the patch.
  • Allow it to settle.
  • After a few minutes check if the filler has settled into the crack. If it does not hold tight, add some more.
  • Smooth out the crack with the help of a trowel
  • Let the patch cure overnight or for the duration recommended by the manufacturer.
  • Check it again to know if it requires an additional patch.
  • It is better to seal the crack after done with patching. This will prevent the absorption of the stains by the concrete.
  • Among the many products available for sealing, heavy-duty water-based urethane stands to be the best.
  • If the surface is smooth, use a roller. If the surface has a rough finish, use a broom or brush with bristles to polish the polyurethane to work into the rough surface.
  • Put on the second layer coating after a few hours. One of the advantages of the polyurethane is that it dries quickly. Another is that it does not smell bad as the other sealants.
  • In heavy traffic areas, apply three to four layers coating of the sealant.


Cracking of concrete is a natural phenomenon and hence inevitable. But you can certainly take measures to increase the lifespan of healthy concrete and reduce the cracking. Some of the points that you should keep in mind while building a concrete structure are:

  • Provide proper spacing and placement of crack control joints and expansion joints.
  • Provide the necessary reinforcements wherever needed.
  • Ensure the concrete mixture is not to wet. Also it should not lose moisture easily and dry quickly. The composition of the mixture should be a proper balance between the two.
  • Proper placement and vibration of concrete.

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Click Here to Leave a Comment Below 1 comments
JHA Australia - February 2, 2022

Great guide that everyone can follow through. It’s best to fix cracks for safety purposes.


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