Concrete blocks are often used in constructing a wide range of structures from homes to commercial properties and outdoor structures. Commonly rectangular, concrete blocks are manufactured as a solid block of concrete or with hollow chambers. Although concrete blocks are strong and durable, cracks sometimes develop. As a home or structure settles, for example, sideways or shifting force can put pressure on the concrete block, resulting in a crack. Fortunately, do-it-yourselfers can fix the damage.
Place a masonry grinding wheel in a small hand-held grinder. Begin at one end of the crack and move the grinding wheel along the entire length of the crack. Attempt to form a V-shaped channel along the length of the crack with the grinding wheel.
Brush out dust and debris from the crack with a stiff-bristle brush. Work the bristles of the brush down into the V-shaped channel along the length of the crack. Blow out remaining dust with a can of compressed air or with air from a small air compressor.
Mix concrete epoxy crack filler in an small plastic container. Follow the manufacturer's directions for mixing. It may be necessary to mix two separate parts of the epoxy together, blending them thoroughly. Add the recommended amount of sand as required to use with a concrete block wall and stir thoroughly with a stir stick.
Dip a trowel into the epoxy and sand mixture. Begin at one end of the crack and force the epoxy into the V-shaped channel along the crack. Continue working along the entire length of the crack. Smooth the epoxy out along the edges of the crack to overlap the solid concrete on the sides. Allow the concrete epoxy filler to cure thoroughly. Depending on temperature and humidity levels, it may take up to eight hours for the epoxy to cure and harden.