Introduction
You should never ignore cracks on your concrete floor. Even a tiny crack can quickly become too big to be easily fixed. Concrete can crack because of climate change, improper mixing ratios, and construction issues.
To fix a crack, start by assessing its type, cleaning it, applying a concrete bonding adhesive, and filling it with epoxy, polyurethane, or a latex-based sealant.
Supplies Needed
Tools and materials:
- Chalk
- Nyalox brush
- Paint brush
- Putty knife
- Plastic sheet
- Caulk gun
- Latex- or epoxy-based concrete bonding adhesive
- Concrete crack filler (epoxy, polyurethane, or latex-based sealant)
Safety gear:
- Goggles
- Respirator
- Fully covered clothing
- Closed-toe shoes
Assess the Crack
Cracks differ in size. Each width, length, or depth of crack will require a different repair approach. Mark the cracked area with a marker or chalk to make sure you don’t miss any spots.
Here are some common types of cracks in concrete to help you find out what you’re dealing with:
- Hairline cracks: Just like the name implies, these cracks are as tiny as a hairline, about ¼ inch. They form when concrete settles and cures.
- Shrinkage cracks: These are formed when the concrete slab dries and loses a lot of water, which causes it to shrink.
- Structural cracks: These cracks are wider than ¼ inch and require immediate fixing to prevent them from spreading.
- Overloading cracks: These are formed when excessive weight is placed on a concrete slab.
- Alkali-silica-induced cracks: When an alkali reacts with sand and stones (which contain silica), cracks form because of the swelling effect of the reaction.
- Joint placement-induced cracks: These cracks form as a result of the wrong placement of gaps or joints in concrete. As concrete shrinks while drying, it needs enough space to control cracking. Insufficient joint spacing leads to cracks.
- Freeze-thaw cracks: When water seeps into concrete pores, it tends to freeze in cold weather and expand. This expansion causes the concrete to crack.
- Heaving cracks: These cracks are formed by internal forces like soil movement or tree roots. Concrete reacts to pressure and cracks because it doesn’t flex.
Clean the Crack
Cracks in concrete often contain debris like sand particles and small concrete fragments. Getting rid of them is important so the repair compound properly adheres to the concrete.
For smaller cracks, use a Nyalox brush to remove dirt and clean them thoroughly. If the crack is large, use a hammer to widen and expose it so you can get rid of the debris inside.
Apply a Concrete Bonding Adhesive
Concrete bonding adhesive helps the repair material strongly attach to the concrete. There are many bonding agents available, but latex- and epoxy-based are the most common types. Here’s how to apply it:
- Make sure there’s no dust inside the crack and it’s dry.
- Use a brush to apply the bonding agent evenly over the surface.
- Some brands require the adhesive to be fully dry before filling, while others recommend applying the filler while it’s still tacky. Follow the manufacturer’s instructions regarding drying time.
Fill the Crack
Choose a filler depending on the size of the crack and its location. Here are some options:
- Epoxy crack filler: Epoxy is best used for structural cracks. Its main ingredient, epoxy resin, is mixed with high-strength concrete or silica and applied inside the crack. Epoxy is highly durable, resists stains, and produces minimal waste after application. It is, however, unsuitable for wet or too hot conditions and is too rigid to be used for active or moving cracks.
- Polyurethane crack filler: Polyurethane is preferably used for non-structural cracks. Unlike epoxy, it is flexible and can be applied in wet and moist conditions due to its water-reactive properties. This makes it useful for repairing water leaks in concrete.
- Latex-based sealants: These are ideal for small, non-structural cracks that are up to 0.5 inches wide. The sealant is applied with a caulk gun to ensure it reaches the base of the crack, and the surface is smoothed with a putty knife.
Finishing Touches
Use a trowel or putty knife to smooth the surface so it blends with the surrounding concrete. Cover the repaired area with a plastic sheet to help retain moisture during curing. Some crack fillers take less than 24 hours to cure, while others take longer. Always check the manufacturer’s instructions for the specific curing time of the product you’re using.
FAQs
How do I know if a crack is structural?
If the crack is wider than ¼ inch, goes all the way through the slab, or if there’s any sinking, then there’s a high chance it’s structural.
Does repaired concrete stand out from the rest of the surface?
It depends on the size of the repair. Small repairs blend seamlessly with the rest of the surface, while larger ones are usually noticeable.
When to Hire a Professional
Fixing cracks in concrete is a simple DIY job that can also be satisfying. However, if the cracks are structural or recurring, it’s best to hire a pro.
If you’re in Adelaide and need help with cracked, chipped, or deteriorating concrete, Swart Plastering has you covered. With over 100 years of experience and award-winning craftsmanship, our pros use high-quality materials for long-lasting results.
