How to Fill Air Spaces in Concrete Block

Air spaces in concrete are not only unsightly, they can pose a safety issue. They are caused when bubbles form during the mixing and pouring process, leaving gaps when the concrete dries. Heavy use or severe changes in weather can also cause concrete to crack, creating a potential tripping hazard. In any case, filling air spaces often doesn't require more concrete. You can get the job done with a simple epoxy fix.

Broom or shop vac
Etching solution
Water
Concrete repair epoxy
Flat edge (metal or plastic)
Epoxy top coat
Paint roller

Instructions

- 1
  Clean the air space with a broom or a shop vac. Dust and debris could result in a poor bond between the epoxy and concrete.
- 2
  Spread etching solution over the air space and surrounding area. This will create a rough surface that will strengthen the bond between the epoxy and concrete.
- 3
  Allow the etching solution to dry. Dry solution will be hard and not tacky to the touch. Brush away any excess debris and dry solution with a broom.
- 4
  Rinse the etching solution with water. This will remove any dust that could interfere with the epoxy's bond to the concrete. Allow to completely dry.
- 5
  Spread the epoxy over the air space with a flat edge or a paint roller, if the space is not too deep. Allow the epoxy to dry for at least 24 hours. Dry epoxy will not be tacky to the touch.
- 6
  Apply the epoxy top coat with a paint roller. This will seal the epoxy, making it weatherproof and protecting it from organic elements that could break the bond.

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