Spalling Concrete? Repair It

Lead Image
  • 4-6 hours
  • Intermediate
  • 100-400
What You'll Need
Circular saw with a masonry blade
Concrete mix
Paddle bit
Wired brush with scraper
Anti-rust paint
Bonding agent
2-by-4-inch board
Plastic sheet
Safety goggles

Spalling concrete, or concrete cancer, is a cosmetic blemish to structures. Spalling requires concrete repair to restore the concrete to its original condition. This article explains how to carry out those repairs.

Spalling is caused by carbonation and occurs on the surface of reinforced concrete structures. Carbon dioxide diffuses with the concrete and reacts with the chemicals inside the concrete. This reaction causes the steel bars inside the structure to corrode and expand. If you catch the spalling in the early stages, the integrity of the concrete structure will not be affected.

If the affected area is minor enough, you can complete the concrete repair by fixing the reinforcing bars inside the structure and resurfacing your project.

Step 1 - Cut around the Spalling

Put on the safety goggles and gloves. Use the circular saw to cut 3/8 inch deep around the damaged area of the concrete structure.

Step 2 - Remove the Damaged Concrete

garage floor with damaged concrete

With your hammer and chisel, begin to chip away at the damaged concrete within the cut-out section of the structure. Remove the pieces of concrete out of your work space as you go along to expose the reinforcing bar beneath the damaged section.

Step 3 - Repair the Reinforcing Bars

Use the wired brush to scrape away all rust from the bars. If you spot more rust beyond the perimeters of your cutout, you will need to perform additional cutting to treat the affected areas.

Step 4 - Apply Anti-Rust Paint

After you remove all rust and corrosion, you will need to apply the anti-rust paint to the reinforcing bars. Apply one generous coat of paint and allow at least 10 minutes of drying time. Then apply a second coat to the bars to prevent future oxidation.

Step 5 - Prepare the Concrete Mix

shovel and concrete in a wheelbarrow

Mix the concrete by adding the required amount of water, according to the manufacturer's instructions. Mix the concrete in the wheelbarrow. Use your drill with the paddle bit to keep the concrete mixed until you get ready to pour it. This technique will keep the concrete from settling in the wheelbarrow.

Step 6 - Apply a Bonding Agent

Apply a bonding agent to the surface of the affected area. This procedure is significant because it allows the old cement to bond closely with the cement that you will pour in the next step.

Step 7 - Pour the Cement

Pour the prepared cement into the cutout of your concrete form until the new concrete is even with the rest of the structure. Use the edge of a 2-by-4-inch board, held at a 45-degree angle, to smooth the surface of the patched area.

Step 8 - Cover the Area

To ensure the patch cures properly, cover the area with a plastic sheet, which prevents the patch from drying too fast. Lift the plastic within 48 hours to mist the concrete with water to help prevent future spalling.