How to Repair Corroded Cement Blocks

Whether they're part of the foundation of your home, the blocks that make up your steps or porch, a wall around your property, or just used as liners around a flowerbed, corroding cement blocks can make your formerly well-tended house look like an eyesore. Before you call in an expensive professional to have all of those crumbling, chipped and pitted cement blocks replaced with new ones, give a college try to refacing them yourself. It is easier than you think, will make those cement blocks look just like new ones and will save you a bundle.

Protective clothing
Work gloves
Safety goggles
Paper mask or respirator (optional)
Hammer
Chisel
Broom
Garden hose
Cement bonding agent
Large paintbrush
Medium bucket
Shovel
Cement patch product
Water
Metal trowel
Small pieces of scrap lumber
Duplex nails
Form release oil
Small tamp (optional)
Plastic tarps
Painter's tape (optional)
Fine-mist spray bottle

Instructions

- 1
  Put on long sleeves, long pants and shoes that completely cover your feet. Don a pair of work gloves and some safety goggles. If your cement blocks have many small particles coming off of them, also wear a paper mask or respirator.
- 2
  Make an indention around the perimeter of the vertical block surfaces that you want to repair using a hammer and a chisel. This will allow the cement patch to “grab” onto the surface.
- 3
  With a broom, sweep the area to remove large pieces of fallen and loose cement, dirt and any other debris. Spray the cement blocks thoroughly using a garden hose to ensure that the surfaces are completely clean.
- 4
  Apply a generous coat of cement bonding agent, using a large paintbrush, onto all of the block surfaces that you are refacing.
- 5
  In a medium bucket, use a shovel to mix together the cement patch product and the amount of water that the package of your particular product requests.
- 6
  Trowel on a 3/8-inch layer of the cement patch, using a metal trowel, over all of the surfaces that you want to reface. Make sure that the surface is smooth and level. Apply more cement patch in deeply damaged vertical areas, once the first layer is soft-set, and smooth the surface well.
- 7
  Create small wooden frames with scrap lumber and duplex nails to fit around horizontal areas that have deep holes that need filled. Coat the frames with a layer of form release oil so that the cement does not stick to them, then set them over the areas that you want to fill.
- 8
  Use the shovel to pour a thin, tightly-packed layer of the cement patch into each of the wooden frames. Make sure that each hole is well-filled. If the frames are large enough, tamp down the wet patch inside of each frame and smooth the surface with the trowel. Let the cement cure for 10 to 30 minutes.
- 9
  Cover the curing cement blocks with plastic tarps for one week. Use painter's tape to hang tarps vertically, if necessary. Remove the tarp and spray the patched areas with water from a fine-mist spray bottle once a day during this week, then replace the tarps. This will maintain an even curing level.
- 10
  At the end of one week, remove the tarps and any frames.

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