How to Fix Cracks in Concrete Floor

Concrete flooring is one of the oldest and most installed durable long-lasting floors. However, cracks, holes, and crevices may develop and at a time may end up being large cracks on your concrete floor slab. But, how do you repair cracks and fix gaps on your concrete patio, basement, and garage floor?

To effectively fix the cracks in concrete flooring, identify the type of crack and its cause. Clean the area, key it and fill it with concrete floor fillers. Once done seal the area and take measures to prevent the recurrence of a crack in your concrete patio, basement, garage floors.

I’ll take a look at the causes of concrete cracks, how to fix such cracks, gaps, and the prevention measures to undertake to reduce the chances of your concrete floor cracking.

Causes of Cracks in Concrete Floor?

Identifying the causes of cracks in a concrete floor is the utmost step to fix it. The common cause of concrete cracks is drying shrinkage. It’s where plastic concrete sets, hardens, and starts to shrink by 12.5% for every 20-feet. All the factor that facilitates drying shrinkage can also trigger and accelerate concrete cracking. In addition, when the internal tensile stress exceeds the tensile strength of the concrete, it can form gaps and crevices on your concrete floor.

The following are some of the reasons why you may develop cracks on your concrete surface:

  1. Too much water in the concrete mix – this causes more drying shrinkage as the extra water evaporates away, thereby increasing the chances of cracks developing on your floor.
  2. Sub-par subgrade- to establish a proper base for your fresh concrete surface, you need to ensure that sub-grade preparation is done the right way; with a smooth, even, and frost-free sub-grade being recommended if you’re looking to avoid concrete settling and cracking. A properly prepared, smooth subgrade inhibits concrete cracking by minimizing restraint during concrete shrinking.
  3. Improper concrete curing- poorly-cured concrete is bound to start cracking at an early age. Concrete curing is usually done to help with moisture retention thus preventing rapid moisture loss that facilitates cracking. As such, if the process is unprofessionally done, the concrete surface is likely to suffer map cracking, whereby the surface concrete shrinks faster than the concrete below the surface due to faster drying. Severe concrete floor cracks due to poor curing usually require repairs as they can compromise the floor’s structural integrity. Curing also helps to inhibit concrete scaling.

Is it Normal for Concrete Floor Slab to Crack?

Yes, concrete floor slabs crack every so often, typically, by 0.5-inches for every 100-feet. As such, no need to worry if you come across very narrow (0.125-inches in width) slab cracks. However, should you spot cracks that are significantly wider than 0.125 inches, then your floor slab’s structural integrity could be compromised and require some repair works?

There are three major types of concrete slab cracks

  • Plastic shrinkage cracks,
  • Drying shrinkage cracks,
  • Structural cracks.

It’s important to recognize which type of cracks you’re most likely to develop on your slab, as each has its own control measures.

How to Fix Cracks in Concrete Floor?

It’s possible to fix the cracks on your concrete patio, basement, and garage floor without breaking a bank. It’s important to fix up any significant cracks on your patio and garage floor as soon as they appear. This will help prevent the cracks widen to the large gaps and holes, which may significantly affect the concrete’s structural integrity and floor durability. What’s more, cracks are an eyesore and reduces the aesthetic value of the floor. Fixing them, therefore, goes a long way towards enhancing your home’s value and overall appeal.

Here’s a simple and fast DIY friendly procedure to seal up shrinkage cracks on your concrete floors;

1. Clean the Cracks Floor Section

oil or grease-based dirt and debris can hamper the efficiency with which concrete filler material bonds with the cement.

See More on How to clean sealed concrete and remove stains?

3. Key the Crack Hole

This can be done through cold-chiseling the crack to make its base larger than the surface. This helps improves the efficiency with which the filler material bonds to the old crack.

4. Sweep or Vacuum the Floor

Sweep the area to eliminate dirt and debris. You can use a soft broom or a dry mop or a vacuum cleaner to completely eliminate any dirt and dust particles that may affect the hole and crevice fix.

5. Apply Concrete Floor Crack Filler

Apply the concrete filler (such as DAP cement filler) along the length of the crack. Once the filler material has settled, finish by troweling the concrete surface to smoothen it out. Let the filler material cure overnight.

Tip: Smaller cracks(1/4 inch wide) are repaired with a concrete caulk or liquid filler.

6. Seal the Repaired Concrete Floor Area

As a final step, seal both the filler/patch and the concrete- as this helps prevent stain absorption by the concrete material. Ensure to use a premium-quality sealer (Armor Solvent Based Acrylic Sealer), or such as a water-based polyurethane sealer.

See more on Best Water Based Polyurethane for Floors.

Here a video of different ways of fixing cracks in concrete floor

How to Fix a Crack in Concrete | A DIY Guide

How to Fill Large Gaps in Concrete Floors

Unlike smaller cracks, wide cracks are best fixed with concrete patching compound. The pathing compond is mixed with water and applied witha a towel, smoothed and textured to blend with the surrounding floor. Its then painted and sealed to completely match with the old flooring.

Yow will require the following tools;

  • Masonry chisel
  • Masonry hammer
  • Wire brush
  • Concrete patching compound

Here’s a procedure of how to fix wide cracks on your concerete floor

  • Remove any furniture to allow disruption. Clean the area thoroughly.
  • Chisel the crack to widen the gap using the chisel and masonry hammer.
  • Clean the area with a wire brush to remove any dirt and debris. you can vacuum the area to remove any water and dirt left.
  • Get your concrete patching compound (such as EPOXY Mortar Patching System) Mix and trowel the pathing compound on the holes or cracks. Stab to remove any air pockets until the cracks are filled.
  • Smoothen and feather the patching compound, Brush off any residue, and allow it to cure completely.
  • Paint and seal your concrete floor with the desired color and hue.

Here a video on how to fix big cracks on your concrete floor

DIY Easy Big Crack Repair In Concrete Floor

Small gaps like hairline cracks may be repaired with caulk or crack filler and even patching compound. You just require a crack elastomeric filler and caulking gun to get rid of such cracks.

how to fix cracked uneven concrete patio

How do I Prevent Shrinkage Cracks on Concrete Floors?

How do I Prevent Shrinkage Cracks on Concrete Floors?

Preventative measures against cracks in concrete flooring can be employed at the concreting stage, or after concrete formation. Here’s how to prevent cracks in concrete floor occurring;

  1. Ensuring there’s no excess water content in the concrete – since the water-cement ratio determines the quality of concrete, a proper water/cement ratio that shouldn’t be exceeded during concreting is ½. Concrete with less water content tends to exhibit enhanced durability.
  2. Ensuring to implement the appropriate concrete mix design – this includes the incorporation of the recommended amounts of concrete aggregates for lower-shrinkage concrete. Also, this includes using the right amount of cement in the water/cement mix.
  3. Ensuring to use high-quality concreting products – your aggregates should be dense, hard, large top sized, and have optimal gradation. Using premium-quality aggregates helps minimize concrete shrinkage. On the other hand, low-quality admixtures like dirty aggregate with enhanced water demands tend to fuel concrete shrinkage.
  4. Ensuring to use the appropriate finishing techniques- proper timing is usually required in between concrete finishing operations as this can affect the chances of developing cracks later on. What’s more, it’s necessary to employ quality finishing methods like flat troweling and flat floating. Finishing techniques to avoid include:
  5. Using vibrating screeds to overwork the concrete – as this leads to the settlement of aggregate.
  6. Finishing on spots where there’s surface bleed water, as this promotes concrete cracking.
  7. Ensuring proper concrete vibration – concrete that’s been properly vibrated is usually free of any entrapped air that may lead to the development of cracks down the line.
  8. Adding contraction joints – these are plastic or hardboard strips that are easier to maintain than concrete floor cracks. Contraction joints are usually placed at strategic spots, taking into account the slab thickness; and installed to strategic depths to ensure optimal efficacy in the prevention of random cracks.

Here’s how to repair cracks in concrete driveway

How To Fix Cracks In Concrete- And Blend In The Repair!

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