Staples Stitch Cracked Concrete Back Together Again
When contractors want to place an overlay on top of existing concrete, cracks are their worst enemy, especially wide, active cracks that can reflect through to the overlay and cause new cracks. Instead of ripping out that badly cracked concrete and starting over, you can now literally stitch the concrete back together using the Concrete Staple from Concrete Product Resource (CPR), Santa Rosa, Calif. As the name implies, this strong steel strut looks just like a giant paper staple, but it’s specially designed to be installed across existing cracks in concrete to keep them from pulling apart, moving side to side, or rising higher on one side. During installation, the staple is embedded in epoxy so it acts like a foundation bolt, providing tensile and yields strengths exceeding Grade 40 rebar.
“Our product physically ties the broken concrete back together with enough strength to make it one piece of concrete again,” says Allan Firestone, the inventor of the staple. “The strength of the staple along with the strength of the epoxy become as strong as the existing concrete and stronger than the surrounding control joints. Think of a broken chain. If you repair the chain with a link that is stronger than the other links, the new link won’t be the one that fails.”
John Marino of Advanced Concrete Supply, Fort Walton Beach, Fla., has used the Concrete Staple successfully on numerous projects. “The staple is the only means we have to repair concrete cracks other than concrete replacement,” he says. “In the past, we have tried epoxy, filling, band aids, fiberglass mesh, and nothing seemed to work. I have checked the first repairs we made using the staple, and they still look like the day we did them.”
How to installTo install the Concrete Staple, you start by saw cutting a slot across the crack to a depth of about ½ inch. Drill two ¾-inch diameter holes to a depth of 2 ½ inches to accommodate each end of the staple, and then pour epoxy to fill the holes and slot about halfway up. Insert the staple and finish by adding a skim coat of epoxy or repair mortar on the top, sprinkling it with sand for better overlay adhesion. The epoxy not only firmly anchors the staple, it also encases the steel to protect it from corrosion.
When working with very thin overlays, you can prevent ghosting of the repair by installing the staples a bit deeper and grinding off any excess epoxy. Cutting new control joints within the overlay pattern will relieve stress and avoid new cracks. Marino recuts the new control joints at least 50% of the concrete thickness.
The staple can also be used to repair uneven cracked concrete if the raised area is no more than ½ to ¾ of an inch. “You can shave down the high area or raise one side with an extra lift of overlay material and then install the staples. Once installed, the embedded staples make the concrete one piece again, which helps keep one side from being able to lift or fall independently,” says Firestone.
The Concrete Staple comes in 12- and 18-inch lengths. To achieve the best results, use the two lengths alternately, spacing the staples 12 to 16 inches apart. For the epoxy, Firestone recommends using a 100%-solids high-strength liquid bonding adhesive, such as Concresive 1090 from BASF.
ApplicationsAlthough the Concrete Staple is used mostly to repair cracks in concrete patios, driveways, walkways, and pool decks in preparation for an overlay, it has other uses as well. “We have also used the staples to stitch cracked retaining walls and foundations, when adding new concrete to old, and to bridge across slots made in concrete slabs for installing drain pipes before we overlay,” says Firestone.
For more information:To view a video of the Concrete Staple being installed and to locate a dealer, visit www.concreteproductresource.com.