How to Repair Cracks in Concrete

Cracks in concrete are a common issue, whether in driveways, sidewalks, patios, or even foundation walls. Over time, exposure to weather, heavy loads, and natural settling can cause concrete to crack, leading to potential structural problems and an unsightly appearance.

Ignoring cracks can allow water to seep in, leading to further deterioration, mold growth, or even foundation issues. Fortunately, with the right materials and techniques, repairing concrete cracks is a manageable task that can prevent more extensive damage in the future.

Common Causes of Concrete Cracks

Before you can effectively repair concrete cracks, it’s essential to understand why they happen. Identifying the root cause will help you choose the best repair method and prevent future cracking. Here are the most common reasons concrete cracks:

Shrinkage Cracks

• Why it happens: When concrete cures (dries and hardens), it loses moisture, causing it to shrink. If the moisture evaporates too quickly, small cracks form on the surface.
• Common locations: Driveways, patios, sidewalks, and walls.
• How to prevent it: Proper curing by keeping the surface damp for several days after pouring.

Expansion and Contraction

• Why it happens: Temperature changes cause concrete to expand when hot and contract when cold. Without proper control joints, the stress leads to cracking.
• Common locations: Exterior concrete exposed to sun and temperature changes.
• How to prevent it: Installing control joints (planned cracks) helps concrete expand and contract without random cracking.

Overloading

• Why it happens: Concrete has a weight limit, and excessive pressure—such as heavy vehicles or machinery—can cause it to crack.
• Common locations: Driveways, parking lots, industrial floors.
• How to prevent it: Use reinforced concrete (adding rebar or wire mesh) in high-traffic areas.

Poor Installation or Mixing Issues

• Why it happens: Improper mixing ratios, weak concrete, or poor finishing techniques can lead to early cracking.
• Common locations: Anywhere concrete was improperly poured or finished.
• How to prevent it: Ensure proper mixing of water, cement, and aggregate, and use professional pouring techniques.

Soil Movement and Settling

• Why it happens: Shifting soil, erosion, or poor compaction underneath the concrete can cause movement, leading to cracks.
• Common locations: Foundations, sidewalks, and driveways.
• How to prevent it: Compact the soil properly before pouring concrete and consider reinforced footings in areas with loose soil.

Identifying Different Types of Concrete Cracks

Not all concrete cracks are the same. Some are purely cosmetic, while others can indicate serious structural issues. Identifying the type of crack you’re dealing with will help you choose the right repair method.

Hairline Cracks

• Appearance: Thin, surface-level cracks (less than 1/16 inch wide).
• Causes: Shrinkage during curing, minor temperature changes, or normal aging.
• Impact: Usually not structural, but they can allow water to seep in, leading to further deterioration.
• Repair Method: Fill with a concrete sealer or patching compound to prevent moisture infiltration.

Structural Cracks

• Appearance: Wider than 1/4 inch, often extending deep into the concrete.
• Causes: Foundation settlement, heavy loads, or soil movement.
• Impact: Can compromise structural integrity and worsen over time.
• Repair Method: Requires epoxy injection or polyurethane filler to restore strength and prevent further damage.

Settlement Cracks

• Appearance: Irregular or stair-step cracks, often found in concrete slabs or walls.
• Causes: Uneven soil settling, improper compaction, or changes in ground moisture levels.
• Impact: Can lead to sinking slabs or misaligned structures.
• Repair Method: May require mudjacking (lifting the slab with a slurry) or foam injection to stabilize the concrete.

Expansion Cracks

• Appearance: Straight cracks often near expansion joints.
• Causes: Temperature fluctuations causing concrete to expand and contract.
• Impact: Can widen over time, leading to surface instability.
• Repair Method: Use flexible sealant to allow movement while keeping out moisture.

Plastic Shrinkage Cracks

• Appearance: Random, spiderweb-like cracks on the surface of newly poured concrete.
• Causes: Rapid moisture loss during curing.
• Impact: Typically superficial, but they can weaken the surface if left unsealed.
• Repair Method: Apply a resurfacer to smooth and strengthen the surface.

Preventing Future Concrete Cracks

Once you’ve repaired existing cracks, the next step is to prevent new cracks from forming. While concrete is a durable material, it is still susceptible to damage from environmental factors, heavy loads, and poor maintenance. Below are the best strategies to extend the lifespan of your concrete surfaces and minimize cracking.

Proper Curing Techniques (Prevents shrinkage cracks)

Why it matters: If concrete dries too quickly, it can develop shrinkage cracks.

How to prevent it:

• Keep newly poured concrete moist for at least seven days by spraying it with water.
• Cover it with plastic sheeting or a curing compound to retain moisture.
• Avoid pouring concrete in extremely hot, dry, or windy conditions.

Tip: Use a slow-curing mix or add a curing agent to improve durability.

Use Reinforcement Materials (Prevents structural cracks)

Why it matters: Reinforced concrete is stronger and less likely to crack under pressure.

How to prevent it:

• Add steel rebar or wire mesh when pouring concrete for driveways, patios, and foundations.
• Use fiber-reinforced concrete to reduce micro-cracking.
• Consider adding control joints to guide cracks into predetermined areas.

Tip: Reinforcement is especially important for high-traffic areas like parking lots and garages.

Install Control Joints (Prevents random cracking from expansion and contraction)

Why it matters: Concrete expands and contracts with temperature changes, leading to stress cracks.

How to prevent it:

• Install control joints (pre-planned grooves) every four to six feet in sidewalks and every ten to fifteen feet in driveways.
• Make sure joints are one-quarter the thickness of the concrete slab.
• Use a sealant in joints to prevent water infiltration.

Tip: If your concrete lacks control joints, cut them in with a saw before cracks develop.

Waterproofing and Sealing (Prevents cracks from moisture and freeze-thaw cycles)

Why it matters: Water seeps into cracks, then expands when it freezes, making cracks worse.

How to prevent it:

• Apply a concrete sealer every two to three years to protect against water and weather damage.
• Use penetrating sealers for driveways and exterior surfaces.
• For basements and foundations, apply a waterproofing membrane to prevent moisture intrusion.

Tip: Seal concrete in spring or fall to allow proper bonding without extreme temperatures.

Regular Maintenance and Inspections (Prevents small cracks from becoming bigger problems)

Why it matters: Catching minor issues early can save time and money on major repairs.

How to prevent it:

• Inspect concrete regularly for signs of cracks, settling, or damage.
• Clean driveways and patios seasonally to remove dirt and debris that can weaken surfaces.
• Reapply sealant if water no longer beads up on the surface.

Tip: Address small cracks immediately with a quick patch to prevent them from expanding.

Contact A-Core for Expert Concrete Repair

For expert concrete repair and maintenance, A-Core Concrete Specialists can provide high-quality solutions tailored to your needs. Whether you need concrete cutting, sealing, foundation repair, or resurfacing, our experienced team is here to help.

Contact A-Core today to schedule a consultation and keep your concrete surfaces in top condition for years to come. Visit A-Core to learn more about our services and request a quote. With multiple locations across the United States, our experienced team is ready to assist you