Spalling is a surface damage on concrete or concrete block structures. It can be caused by fire damage, freezing and thawing cycles or moisture-damaged rebar. Spalling walls may be flaky or chipping, and may even have minor holes or voids on the surface. Fortunately, spalling is primarily associated with cosmetic damage, and is not a sign of structural problems within the wall. This means that spalling walls can be repaired to create an attractive finish. Does this Spark an idea?
Instructions
1. Remove loose or flaking concrete. Brush the spalling area with a stiff wire brush to help remove some loose material. Scrape away any additional loose concrete using a paint scraper, or hammer it out with a chisel.
2. Repair holes or voids. Mix epoxy concrete filler according to the manufacturer's instructions. Use the epoxy to fill holes or voids in the wall, then smooth them with a trowel so they are even with the rest of the surface. Allow the patched area to dry for 2 to 3 hours before proceeding.
3. Use a lime-based mortar mix to cover the walls. The mortar will be applied like plaster to give the block a smooth finish, and is commonly known as "parging." It will also help prevent future spalling. Lime-based mortar is fairly permeable, and will allow the block to breathe. Traditional cement mortar is not permeable, and will trap water in the concrete. This will cause future damage that can lead to structural problems with your block wall.
4. Blend your mortar mix with water according to the directions on the package. Use a drill with a paddle bit to stir the mixture thoroughly in a bucket or wheelbarrow.
5. Apply the mortar to the block wall using a trowel. Keep the application about 3/8" thick, but don't worry about texture or appearance at this point. Wait until the mortar starts to harden, then use a stucco or plasterer's rake to scratch lines in the surface of the mortar. These grooves will help hold the final coat of mortar in place.
6. Mix and apply a second coat of lime-based mortar. This coat should be roughly 1/4" thick. You can create a smooth or textured finish using your trowel and a putty knife, though it may take a bit of experimenting to get the wall truly smooth.
Tags: holes voids, block wall, lime-based mortar, permeable will, structural problems
