Cinder blocks, or blocks typically constructed of concrete and coal cinders, are a construction material used in the formation of foundations and walls. Cinder blocks can develop cracks over time due to environmental factors or building settling. You can fix cracks in a cinder block wall using a type of glue called epoxy. Repairing a cinder block wall with epoxy may take some time and preparation, but a few basic tools, including a hammer and chisel, should help you complete the task.
Use a measuring tape to measure the size of any existing cracks in the cinder block wall. The cracks to be repaired must equal a depth of at least ½ inch and a width of at least ¼ inch in order to properly apply the epoxy. If a crack isn't these dimensions, strike the edges of the crack with a hammer and chisel to widen it. Place the chisel in the crack and strike the chisel with a hammer to increase the depth of the crack.
Use a stiff-bristle brush to brush off inside and around the crack. This will help remove any sediment or moss in the area, as well as any cinder block pieces that may be lodged in the crack.
Attach a nozzle hose to a shop vac. Switch on the shop vac and point the end of the hose at the area of the crack. The hose should suck up any residual sediment or cinder block pieces that weren't previously removed by the stiff-bristle brush.
Prepare concrete epoxy filler in a bucket according to the manufacturer's instructions. Prepare another batch of concrete epoxy filler in a second bucket. Add two parts sand to one part concrete epoxy filler in the second bucket, and mix the contents thoroughly.
Use a paintbrush to apply the pure concrete epoxy filler in the first bucket to the cracks. Spread only a thin layer of the pure epoxy filler on the cracks. Scoop up the sanded concrete epoxy filler in the second bucket, using a trowel. Spread the second filler along the cracks with the trowel. Fill the cracks with the sanded epoxy filler.
Scrape off any excess filler with the back of the trowel while the epoxy is still fresh. Allow the epoxy to dry for the manufacturer-recommended amount of time.