Block walls generally require little to no upkeep or maintenance. Although that may not be a consolation to you when your block wall has a problem, you can fix it without calling a contractor or building new block walls. The type of deterioration -- and therefore the repair -- depends on the damage that occurred.
Spalled and Eroded Block Walls
Use an air hammer or hand chisel to remove all the fractured and loose concrete from the walls. Stop when you reach the rebar or steel inside the block walls.
Investigate the steel for any damage, then clean and/or repair the exposed steel.
Sandblast the concrete surface to roughen it up. You can also use a wire brush if you don’t have a sandblaster.
Create a mixture of two parts masonry sand, one part Portland cement and 10 percent hydrated lime. Patch the deep holes, then let set. Saturate the entire block with water, then wait for 1 to 2 hours.
Spread the plaster over the block walls in layers until it’s approximately three-eighths of an inch thick. Let cure.
Fixing Individual Blocks in the Walls
Use a drill with a masonry bit to make holes in the face of the block you’re repairing.
Chip away at the block using a small sledgehammer and brick set until you see the mortar and the interior of the block.
Place a concrete block on loose soil or sand. Gently use the brick set and small sledgehammer to mark each side of the block. Repeat the cuts -- striking harder along the lines -- until the brick falls apart. Make as many brick faces as you need to fix the wall blocks.
Mix a small amount of mortar mix using a trowel and bucket. Insert mortar mix along the edges of the opened area of the block wall. Place the new block face in the opening. With the trowel’s tip, push mortar in the edges of the block, then smooth it down with a jointing tool. Let cure. When dry, scrape some residue away.