Every home has some concrete around it or under it in the form of a foundation, driveway, sidewalk or patio. Exterior concrete is very visible to passers-by and the neighbours so most homeowners take pride in maintaining and repairing concrete around their home.
Improperly mixed concrete, troweling too soon or over troweling can cause problems with finished or cured concrete. Surface flaws develop.
Dusting appears on concrete surfaces as a fine powder that is easily rubbed off. To treat it, brush the surface, and then apply a commercial concrete sealer, making sure that you follow the directions on the package. This water-like product is available from building supply outlets and concrete speciality stores. Most products are formulated from chemicals and silicone that actually “soak” into the surface of the concrete and crystallize in the pores which hardens and seals the surface, eliminating the dusting problems in most cases. For severe cases, coat the concrete with a surface hardener before sealing it.
To stop scaling — surface mortar peels off — apply two coats of a 1:1 solution of boiled linseed oil and turpentine. Keep off the surface until it has dried. For at least three years, repeat the treatment before winter starts.
When repairing cracks in concrete, make sure the damaged area is free of dirt and debris. With a hammer and special-tempered cold chisel, (wider at the bottom than the shank) chip away the loose concrete. Hold the chisel at a 45-degree angle and undercut the crack so that it is wider at the base than the surface. Remove the debris with an air compressor or shop vacuum.
An acceptable way of repairing minor cracks is to apply a one-part urethane caulking compound. One brand name is Vaulkum which is basically the same colour as concrete. Cracks up to a half-inch wide can be repaired. If the crack is deeper, it can be filled with material as simple as fibreglass insulation or other recommended fill, stopping the fill material a half-inch from the surface. This will prevent the caulking from disappearing.
Once the caulking has cured, it will bind well to the concrete. If you have applied a smooth bead, the crack may be practically unnoticeable.
The advantage of repairing the cracks with this caulking compound is that it remains flexible and will allow the concrete to move or heave slightly, without breaking the seal.
Epoxy or latex patching compounds cost more than patching mortars, but they form a stronger bond and do not require a bonding agent and are self-curing.
For further information, contact a local concrete repair dealer.