How to Fix Deteriorated Blocks

Cover the surfaces around the concrete blocks to protect them from falling concrete. Use plastic tarps for floors and outdoor spaces; concrete may harden over and kill grass and flowers. Cover fixtures such as countertops with newspaper secured with masking tape and remove any nearby portable items.

Work on one deteriorated area of the blocks at a time; the area must remain damp as you apply the concrete. Mist the first area lightly with plain water from a spray bottle. The area should feel wet to the touch but not drip.

Gather some prepared concrete patch on a flat trowel and apply it to the dampened area. Work the concrete patch into deeply crumbled areas with the corners of the trowel. Build the concrete up until it's level with the undamaged areas of the block, or a little higher.

Hold the trowel at a 45-degree angle and drag the edge diagonally across the surface of the concrete block to scrape off excess concrete patch. Smooth the top with the flat of the trowel, if necessary. Continue repairing the remaining deteriorated areas of the blocks.

Texture the surface of each patch once it has set for approximately two to three hours. Place the flat of a 2-by-4 board against the patch and rub it back and forth over the entire surface; this process helps the new concrete blend in with the concrete block around it. Cover each finished patch with a cut square of sheet plastic and let them dry five days before exposing the patches.