Are the unsightly cracks on your concrete floor putting a dent to your otherwise magnificent interior décor? Or maybe, the numerous cracks on your concrete patio and driveway have dampened your curb appeal.
In this article, we’ll take you through the common causes of concrete cracks, how to repair such cracks and prevention measures to minimize the chances of your concrete floor cracking.
Why is my concrete floor cracking?
The most common cause of concrete cracks is drying shrinkage, whereby plastic concrete sets, hardens and starts to shrink by 12.5% for every 20-feet. Any factor that facilitates drying shrinkage can- therefore- fuel concrete cracking. Also, anything that causes the internal tensile stresses to exceed the tensile strength of the concrete, can lead to cracks in your concrete flooring.
The following are some of the reasons why you may develop cracks on your concrete surface:
- 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.
- 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.
- 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, you’re likely to come across very narrow slab cracks that are no wider than 0.125-inches in width. However, should you spot cracks that are significantly wider than that, then your slab’s structural integrity could be at stake and you definitely need to consider doing some repair work.
The three major types of concrete slab cracks include; plastic shrinkage cracks, drying shrinkage cracks, and 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.
Can you Fix Cracks on Concrete Floors?
It’s important to close up any significant cracks on your concrete surfaces before they widen to the point of significantly affecting the concrete’s durability and structural integrity. What’s more, cracks are an eyesore, and fixing them goes a long way towards enhancing your home’s overall appeal.
Use this fast and simple DIY procedure to seal up shrinkage cracks on your concrete floors:
- Clean up the cracked floor section- oil or grease-based dirt and debris can hamper the efficiency with which concrete filler material bonds with the cement.
- Key the crack hole– this is done by cold-chiseling the crack to make it’s base larger than the surface, subsequently helping improve the efficiency with which the filler material bonds to the old crack.
- After keying, sweep the area to eliminate dirt and debris, then apply the concrete filler/patch 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.
- 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, such as a water-based polyurethane sealer.
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. They include the following:
- 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.
- 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.
- 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.
- 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:
- Using vibrating screeds to overwork the concrete– as this leads to the settlement of aggregate.
- Finishing on spots where there’s surface bleed water, as this promotes concrete cracking.
- 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.
- 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.