Concrete Maintenance and Repair
Moisture is the chief enemy of concrete. You can minimize moisture damage and improve the appearance of your concrete surface at the same time by painting or sealing it. Either solution entails periodic reapplications. To test whether the concrete needs a new coat of sealer, sprinkle water on the surface. If the water soaks right in, it's time to reapply. On aggregate-concrete surfaces, use an aggregate sealer. It prevents freeze-thaw cycles from popping out the stones.
Other common problems include stubborn stains, rotting expansion joints, and cracks. These are generally small problems that don't call for removing the slab. More serious surface trouble calls for resurfacing. Be sure to consider door height before adding a new surface.
Varies from an hour or so to several, depending on the repair
Stiff brush, paint roller, bucket, cold chisel, small sledgehammer, metal trowel, caulk gun, tamper, pointing trowel, garden hose, paintbrush, hammer, wheelbarrow, mason's hoe, control jointer, edger, broom, bull float, darby, wood or magnesium float (varies with repair), vacuum cleaner, aviation snips, china marker, circular saw and masonry blade, scrap wood, small piece of plywood
Cleaning, applying patching concrete
Muriatic acid, acrylic or silicone sealer, expansion strip, bonding agent, patching compound, 2x lumber, wire mesh, concrete, burlap, rubber silicone or polyurethane sealant, latex mortar
A stiff brush and a strong cleaning solution will remove most concrete stains. For stubborn stains, use 1 part muriatic acid added to 9 parts water in a bucket. Scrub the area with a stiff push broom. Muriatic acid is caustic -- wear rubber gloves and eye protection. Rinse the slab with water.Cleaning and Sealing: Step 2
To seal concrete, apply a clear acrylic or nonyellowing silicone sealer with a short-nap roller. Let it dry 48 hours.Pro Tip: Keying a crack
To key a concrete crack, chisel it wider at the bottom. A keyed crack helps keep a patch from popping out. Press patching concrete into the opening, then trowel the surface smooth.Replacing expansion joints: Step 1
Expansion joints allow sections of a concrete slab to shift independently so the slab won't crack. The joints are filled with a fibrous material that acts as a cushion. Over time it may deteriorate. If the expansion strip has rotted, chisel it out with a small sledgehammer and cold chisel. Remove all the loose pieces and vacuum out the joint.Replacing expansion joints: Step 2
Buy a new expansion strip and cut it to size. Slide the new strip into the joint and tap it with a piece of wood scrap until the top is 1/2 inch below the concrete surface. Caulk the joint with a rubber silicone or a polyurethane sealant.Repairing pop-outs: Step 1
Enlarge the popped-out area and key it with a cold chisel and small sledgehammer. Clean the hole with a stiff brush.Repairing pop-outs: Step 2
Mist the surface and brush in a latex or acrylic bonding agent. Following the manufacturer's instructions, let the bonding agent dry. Some solutions will get tacky, others will not.Repairing pop-outs: Step 3
Mix up a small amount of patching cement and pack it into the hole. Smooth the surface with a trowel. Keep the area moist until the patch cures.