How do I Repair Concrete Due to Cracking & Spalling?
After much labor to mix and pour a concrete surface, it is extremely frustrating to see it develop cracks or spalling, which is thin layers of concrete flaking off the surface. The most common causes of cracking and spalling are over-mixing, inadequate curing, poor aggregate and freezing temperatures before the concrete sets.
Instructions
Repairing Thin Concrete Cracks
1. Brush the edges of the crack and 2 to 3 inches beyond with a wire brush to rough up the surface.
2. Sweep away dirt, dust and debris with a small broom.
3. Squeeze out a line of epoxy-based concrete repairing compound to the crack.
4. Use a flexible putty knife to forcefully press the repair compound deep inside the crack.
5. Squeeze a second line of compound over the crack and use the putty knife to spread the compound and smooth the surface.
Repairing Wide Concrete Cracks
6. Hit a cold chisel with a masonry hammer along the edge of the crack to break off loose concrete.
7. Hold the chisel at a 45-degree angle and hit with a hammer to cut under the edge and widen the base of the crack.
8. Brush the crack with a wire brush to remove loose bits of concrete. Sweep the dirt and debris away.
9. Apply an epoxy-based concrete bonding agent to the inside of the crack all the way down to the base and extending 3 to 4 inches past the crack.
10. Mix concrete in a wheelbarrow or trough, use a trowel to scoop wet concrete into the crack and press the concrete all of the way down to the base and under the edges. Smooth the surface with a trowel, feathering the edges 3 to 4 inches past the crack.
Repairing Spalling Concrete
11. Break up the spalling concrete with a masonry sledgehammer and remove the concrete dust and pieces.
12. Brush the area with a wire brush or use a masonry grinder for large areas to expose salvageable concrete. Sweep up debris.
13. Roll an epoxy-based concrete bonding agent on the surface with a long-handled paint roller.
14. Mix concrete in a wheelbarrow or trough or call for a concrete pour from a concrete delivery company, depending on the size of the spalling area.
15. Pour the concrete over the surface. Use a trowel to make it smooth, level and match the height of the existing surface.
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