Repairing a concrete slab takes several days to complete. Cracks and chipping of the concrete slab are the two most common problems that occur with this material. Both problems require a slightly different repair method to effectively fix the slab.
Address any shifting that caused the crack in the first place. Drill two inch wide holes every six feet around the diameter of your concrete slab. Dig the holes three feet away from the slab itself. Fill the holes with gravel. Use a soaker hose to soak the gravel for 24 hours. During dry seasons, repeat the soaking process. This helps the concrete slab sink evenly into the ground.
Fill a caulk gun with cement epoxy filler. Fill the cracks with the filler. Use a trowel to smooth out the filler over the surrounding slab. Allow the area to dry for 24 hours.
Mix one part Portland cement and 2.5 parts sand with enough water to make a mud-like texture. Dampen the slab before spreading the mixture thinly over the seams in the concrete. Use a 6 foot straightedge to feather the cement into the rest of the slab to hide the crack. Allow the cement to dry for 24 hours.
Use a electrical saw with a masonry blade to cut out the damaged areas of the concrete slab. Make four cuts around the perimeter of the damaged area. Wear ear, eye and mouth protection as you work.
Take the chisel and hammer and use them to chip the loose cement out from the slab's surface. Brush the loose cement out of the hole.
Mix the cement mixture together with acrylic fortifier and pack it into the hole with a wood float. Try to feather the edges of the hole against the top of the slab. Comletely smooth the top of the hole.
Allow the cement to dry until it feels as firm as a grapefruit. Press the sponge float over the patched area to create a texture to match the rest of the texture on the concrete slab.
Cover the top of the patch with plastic for two days. This will slow the drying process and prevent cracks.