How to Repair Cracks in a Concrete Driveway

Driveways endure a constant cycle of thermal expansion and contraction, which inevitably leads to the spiderweb cracks that mar a clean slab. Left untreated, these fissures become highways for water to seep beneath the concrete, eventually causing frost heave and deep-seated structural failure during the winter months. Repairing them is less about heavy construction and more about methodical surface preparation. When you do the work well, the repair becomes virtually invisible and creates a watertight seal that prevents minor cracks from turning into crumbling craters. Focus on the cleanliness of the crack itself, as any remaining debris will prevent the sealant from creating the permanent bond you need.

  1. Scrub and Vacuum First. Use a wire brush to scrub the loose concrete and dirt out of the crack. Follow up by using a shop vacuum or a leaf blower to remove all fine dust and grit from the crevice.
  2. Grind to Quarter-Inch Width. If the crack is hairline, use an angle grinder with a diamond masonry blade to widen it to at least a quarter-inch. This gives the sealant enough space to form a flexible, durable bond.
  3. Wash and Wait 24 Hours. Wash the crack with a pressure washer or a stiff-bristled broom and water to remove any lingering concrete dust. Allow the crack to dry completely for at least 24 hours before moving to the next step.
  4. Nestle the Foam Base. Press the foam backer rod into the crack until it sits about half an inch below the surface. This creates a bridge that forces the sealant to bond only to the sidewalls of the crack, allowing for movement.
  5. Fill Bottom to Top. Cut the tip of your polyurethane concrete sealant tube at a 45-degree angle. Dispense the sealant steadily into the crack, moving slowly to ensure you fill the void from the bottom up without creating air bubbles.
  6. Trowel Flush and Smooth. Use a margin trowel or a putty knife to smooth the sealant flush with the driveway surface. Apply light pressure to force the material against the edges of the crack for a tight, professional seal.