Concrete Cracks, What Causes Them & How to Fix Them

1. Shrinkage Cracks

• What Causes Them: Shrinkage cracks are one of the most common types of concrete cracks and typically appear soon after the concrete is poured. As concrete cures and dries, it loses moisture and undergoes slight shrinkage. If the surface dries too quickly or if too much water was added to the mix, cracks may form. These cracks are usually small and appear as hairline cracks on the surface.
• How to Fix Them: Shrinkage cracks are generally cosmetic and don’t affect the structural integrity of the concrete. They can be filled with a concrete filler or sealant to prevent water infiltration and improve the surface’s appearance.

2. Temperature Changes and Freeze-Thaw Cycles

• What Causes Them: Temperature fluctuations can lead to expansion and contraction of concrete. In colder climates, freeze-thaw cycles are a common culprit. When water seeps into small cracks and freezes, it expands, causing the cracks to widen over time. This process repeats with each freeze-thaw cycle, leading to more extensive cracking.
• How to Fix Them: For smaller cracks caused by temperature changes, a flexible sealant designed for concrete can fill the gaps and prevent water infiltration. For larger or deeper cracks, it may be necessary to use an epoxy or polyurethane filler. In some cases, resurfacing the area or applying a protective sealant to prevent future freeze-thaw damage may be recommended.

3. Settlement and Soil Movement

• What Causes Them: Concrete can crack due to movement or settling of the soil underneath it. This issue often occurs in areas where soil is prone to shifting or compacting over time, which is common with clay soils or areas with inconsistent moisture levels. As the soil shifts, it can create voids beneath the concrete, causing it to crack or sink.
• How to Fix Them: Repairing settlement cracks often requires addressing the underlying soil issue first. For minor settlement, patching the cracks with concrete filler or caulk may be sufficient. In more severe cases, professional methods like mudjacking or slabjacking may be necessary to lift and level the concrete. These techniques fill voids beneath the slab and stabilize the surface to prevent future cracks.

4. Overloading and Heavy Traffic

• What Causes Them: Concrete is designed to support heavy loads, but over time, excessive weight can cause cracking, especially in areas that weren’t intended for heavy traffic. For example, driveways or walkways may crack if exposed to vehicles or machinery that exceed the concrete’s weight-bearing capacity.
• How to Fix Them: Repairing cracks caused by overloading involves assessing the extent of the damage and reinforcing the concrete if necessary. Small cracks can be filled with a strong epoxy filler, while larger cracks may require partial or full replacement of the affected area. Preventive measures, such as distributing heavy loads more evenly, can help avoid further damage.

5. Corrosion of Reinforcement Steel

• What Causes Them: In reinforced concrete structures, steel rebar is used to add strength and stability. However, if water seeps into the concrete, it can cause the steel to rust and expand, leading to cracks around the reinforcement. This is often referred to as “rebar blowout” and is more common in concrete exposed to salt, such as in winter or near coastal areas.
• How to Fix Them: Repairing cracks due to rebar corrosion may require removing the damaged concrete, treating or replacing the rusted steel, and refilling the area with fresh concrete. This type of repair is more complex and may need the attention of a professional to ensure that both the concrete and reinforcement are structurally sound.

6. Plastic Shrinkage Cracks

• What Causes Them: Plastic shrinkage cracks develop during the initial drying phase of the concrete. These cracks occur when the surface moisture evaporates faster than the internal moisture can reach the surface. Hot, dry, or windy conditions can accelerate evaporation, leading to shrinkage cracks before the concrete has fully set.
• How to Fix Them: Plastic shrinkage cracks are typically superficial and can be filled with a concrete patch or sealant. To prevent future cracks, contractors can cover the surface with a plastic sheet or apply a curing compound to slow down evaporation during the curing process.

How to Prevent Concrete Cracks

While it’s not always possible to avoid concrete cracks entirely, there are steps you can take to minimize the risk:

• Use Proper Mix Ratios: Adding too much water to the concrete mix can lead to excessive shrinkage and cracking. Using the correct mix ratio helps maintain the concrete’s strength and stability.
• Install Control Joints: Control joints are placed at regular intervals to allow for natural expansion and contraction. These joints help direct cracks along specific lines, reducing random cracking on the surface.
• Cure the Concrete Properly: Proper curing techniques help concrete gain strength over time. Keeping the surface damp and covered during curing can prevent rapid drying and reduce shrinkage cracks.
• Seal the Surface: Applying a sealant to the surface protects against moisture infiltration, freeze-thaw cycles, and staining, helping to extend the life of your concrete.
• Address Soil Stability: Proper soil preparation and compaction can help prevent settlement and movement, reducing the risk of cracks caused by shifting soil.

Bethel Custom Brick – Your Concrete Repair Experts in the Detroit Metro Area

At Bethel Custom Brick, we understand that concrete cracks can compromise both the appearance and safety of your property. Serving the Detroit Metro area, we offer professional concrete repair and replacement services tailored to meet your specific needs. Whether you’re dealing with shrinkage cracks, settlement issues, or rebar corrosion, our skilled team can provide durable solutions that restore the strength and longevity of your concrete surfaces. Contact us today to schedule an inspection and learn how we can help protect and enhance your concrete.