Q: Why do my concrete countertops crack? And how do I fix hairline cracks in concrete slabs? Should cracks in concrete be sealed?

A: Repairing hairline cracks in concrete can be a real challenge. However, what clients really care about is that those cracks aren’t visible not impact the countertop’s performance. Structural cracks shouldn’t be present in those well-made concrete countertops. Nevertheless, concrete countertops cracking is possible and is not a sign of poor quality.

Why Do My Concrete Countertops Crack?

Stress causes both hairline cracks and larger structural cracks. When tensile stress builds up in the concrete and surpasses the capacity of the material to resist those stresses, a crack appears. On the other hand, many large structural cracks in countertops occur due to flexing, possibly because a faucet was tightened excessively.

Commonly, concrete hairline crack repair is more difficult. These cracks appear due to shrinkage, either from heat or from drying. As they usually occur near the surface, they can’t be prevented by reinforcing, so using a good mix design with low shrinkage tendencies is the best way to prevent them. Even so, hairline cracks can occur and locate near areas of moisture like dishwashers and sinks. This is because dry concrete is frequently absorbing moisture and then dries out. These wetting and drying cycles will lead to concrete countertops cracking.

If They’re Not Exposed to Humidity, Why Do My Concrete Countertops Crack?

Another cause of hairline cracking is heat exposure; being more related to the time of heat exposure than to the intensity of the heat. Pots don’t get too hot; however, they do remain in one spot for several hours, expanding the concrete with the heat. The more the concrete heats up and expands, the greater the thermal stress is. Commonly, not only is the heating what causes cracking, but also the following cooling that makes the concrete shrink and crack.

Fix Concrete Cracks

Repairing hairline cracks in concrete involves filling the crack with a bonder, restoring the countertop’s appearance, and prevent the penetration of liquids that could stain the concrete. Moreover, the ideal repair material should be more flexible and stronger than the concrete, so future cracking is prevented.

As repairing concrete cracks takes patience, practice, skill, and a good eye for color matching, the process isn’t easy. However, it’s definitely one of the ways to improve your home without shelling out lots of cash. Since a hairline crack is one that hasn’t opened up, which means the room is too little to fill it with anything except for a very low-viscosity liquid. Sealing and concealing the crack are the main goals of a repair since most hairline cracks don’t affect the countertop’s structural integrity.

Before repairing the crack, stains must be removed, as it might be possible to use more fresh sealer down in the crack if it’s unstained. To protect the concrete, the sealer can be rubbed in with gloved fingers. The ideal sealer will have low surface tension and low viscosity, so it gets to penetrate deeply into the crack and wet out the concrete.

Furthermore, a sealer with high solids content will ensure that the material left in the crack doesn’t shrink, pull away, or even leave a void. If you can get it into the crack, a highly fluid epoxy will fill and seal a crack nicely. However, consider that materials like epoxy are efficient because they wet out the concrete, which helps to draw the epoxy into the crack, but this can make the crack look darker.

Since it’s easier to get materials into large cracks, they’re easier to repair. There are sealers/crack fillers in the market, but the final result won’t be considered acceptable for concrete countertops in terms of appearance.

Commonly, crack repair materials for concrete countertops are polymer-modified cement grouts, silicone or latex caulking, or epoxies. Despite each one has its pros and cons; they can easily be color-matched to blend with the concrete.

During concrete countertops’ manufacture, polymer-modified cement grout is the classic material used to fill voids and pinholes. This material can be difficult to work into tight hairline cracks, and it commonly covers the hairline crack’s surface without bonding the concrete together. As cement grout isn’t very flexible and it needs to be sealed to prevent staining, future cracking could be expected.

Despite it must be forced into hairline cracks, silicone or latex-based caulk is somewhat easy to work into cracks. Caulk will degrade over time, especially in wet areas, as it can react with bare concrete. Therefore, it might be necessary to seal the crack with a low-viscosity sealer prior to filling the crack with caulk.

A good choice for filling cracks is epoxy designed for laminating natural stone. It’s commonly available in two viscosities: knife grade and flowing grade. While knife grade is thick like Vaseline, flowing grade is thinner and penetrates cracks on its own quite easily. Since epoxy is a two-component adhesive and it’ll need to be applied quickly after the components are mixed, it’s best to tint one component before blending the two of them to get the color right without any rush. According to the instructions, measure out both components and then choose the opaquest component. Afterward, add dry concrete pigments, epoxy dye, and blend until the color matches the concrete. Once the color meets your expectations, mix the tinted component with the other.

Conclusion

After giving your kitchen a quick look, you get a strong feeling that your kitchen needs to be renewed. Are either replacing your countertops or painting your cabinets the only way to go? Not really. Before replacing your countertops consider there are different ways to fix concrete cracks and multiple original options to redo your countertops without replacing them. Not only are these DIY projects to improve your home countertops, but they will also help you save lots of money.