Cleaning and Repair of Driveways and Walks
By T. Jeff Williams
Your concrete driveway and walk will eventually crack. It's what concrete does. But there are a few things you can do to lessen the impact, namely keep the driveway clean and the cracks filled in.
Sometimes the situation can worsen, such as a major hole appearing in a driveway or walk. This is still reparable and you can do the work yourself. OSH carries a wide selection of cleaning and repair products from Quikrete that will suit your needs exactly. Here's how you get started:
Cleaning Driveways and Walks
Oil spills: Commercial cleaners such as Quikrete Concrete Cleaner works well, but here's a home remedy that will also do the job without having adverse runoff affects on nearby waterways. Its kitty litter and cola. For a fresh oil spill, use kitty litter to absorb the oil. For old stains, coat the area liberally with kitty litter and then grind it into the oil stain with the heel of your foot or a hammer. Once pulverized, pour a can of cola over it all and let it sit overnight. Oil stains will never completely disappear, but two or three treatments may significantly lighten them.
General cleaning: For a traditional cleaning, wet the driveway and then scrub with a detergent and stiff push broom. But you can do a better job faster with a rented pressure sprayer. Hold the spray head about 6 inches or so above the concrete and move it steadily back and forth, overlapping slightly on each pass. The spray will also loosen oil particles embedded in concrete. If the driveway or walk has cracks that need repair, blast out all the dirt and debris first with the pressure sprayer.
Concrete Repairs
Concrete cracks because it moves. It moves because it settles or is pushed up by ice or tree roots, or jostled by earth movements. Putting a heavy vehicle on a driveway adds to the strain. Cracks should be repaired, particularly in areas with subfreezing winters where ice can keep widening them. Small cracks can be filled with acrylic latex caulking that will remain flexible. Larger holes are filled with a ready-mix concrete patch.
Basic Crack Repair Steps:
1. For cracks 1/2-inch or wider, use a hammer and cold chisel to undercut the sides of the crack, essentially leaving a little
overhang. This is a keyway that will hold the patch in place. This is not necessary for hairline cracks.
2. Clean the crack thoroughly with a wire brush or narrow blast of water. Patch material will not adhere to dirt or grease.
3. Apply a thin layer of concrete bonding agent. This is not essential on smaller cracks, but is a must for large holes. It helps
the new repair material adhere tightly to the old concrete.
4. Apply the patch material. When using a latex caulking patch, apply only to a depth of 1/4-inch at a time. Each layer must be
allowed to cure properly or the patch will not hold.
5. Level the final layer with a steel trowel for a smooth finish or with a wood trowel for a textured finish.
6. Cure the patch by covering it with plastic that is duct taped around the edges to prevent air from rapidly drying the patch. For acrylic latex patches, leave the plastic cover on for two days and avoid driving on the patch for another two days. See below for curing concrete.
Repair Materials
Hairline cracks: Quikrete's Gray Concrete Seal is a good choice for cracks up to 1/4-inch wide. It's a liquid that is simply squeezed from the dispenser. It is not necessary to undercut the sides of the crack. Overfill slightly to allow for shrinkage. If a second layer is needed, wait 24 hours.
Wider cracks, to 1/2-inch: An excellent choice here is an acrylic latex formulation that comes in caulking tubes, such as Quikrete concrete repair No. 8620. It can also be used on vertical surfaces, such as concrete retaining walls. No bonding agent is necessary. Clean the crack thoroughly, make sure it is dry and then use a caulking gun to inject a layer of repair material. Keep each layer to a maximum of 1/4-inch thick and allow it to cure completely, as described in No. 6 above.
Holes in concrete: A hole in concrete that wide and deep should be repaired with actual concrete. There are bags of ready-mix patching material at your nearest OSH. The first step is to undercut the edge all around the hole with a hammer and cold chisel. Be sure to wear eye protection. Clean the hole very thoroughly with brush, shop vac or a blast of water. When you apply a concrete patch, the old concrete should be wet (but no puddles) so it will not draw moisture from the patch and weaken it.
Make the patch: For holes, use a bonding agent to make the old and new concrete bind tightly. You can use a commercial bonding agent or make your own by mixing mortar and water to the consistency of paint and brushing it over all surfaces in the hole. While the bonding agent is still tacky, apply the ready-mix patch. This consists of gravel, sand, Portland cement mixed with enough water to make a thick but pliable paste. Trowel it into the hole and then smooth the top with a wood trowel to force the gravel below the surface. Stop troweling as soon as the gravel has been depressed and there is just a smooth layer of concrete and water on the surface. Overtroweling will weaken the surface of the patch.
Cure the patch: Concrete takes longer to cure than an acrylic patch. Cover the patch with plastic taped down around all the edges and let it set for 72 hours minimum. When you remove the plastic, keep the patch damp for another two days by spraying it regularly. Don't drive on the patch for four days.