Concrete can deteriorate for any number of reasons. Poor installation is a common culprit, with not enough attention paid to the subbase, matching the application to the cement product, or the location of expansion joints. Concrete expands in the heat and contracts in the cold. If the expansion joints are not spaced properly, the stress caused by the expansion and contraction will result in cracking.
There are occasions, then, when repair definitely isn’t an option. “If the subbase is eroded, then the concrete section will have to be cut out and a new subbase put in and compacted,” relates Frank Owens, Quikrete vice president of marketing. “Large cracks are problematic, too, especially those that extend all the way through to eventually erode the subbase. They will let in water and the freezing and thawing cycles will ultimately find the weak points in the concrete and create further deterioration.”
Owens notes that if subbase isn’t an issue, then the decision to repair or replace may come down to expense. “It costs from $3.50 to $5.50 per square foot to replace concrete,” he says. “However, leaving the old concrete in place and applying a concrete resurfacer with a squeegee reduces the costs substantially. Material cost for the resurfacer would be about $.25 per square foot. Depending on the extent of surface scaling, the only surface preparation would entail pressure washing.”
It’s not just exterior surfaces that deteriorate over time. Interior floors can become uneven from settling or just plain wear and tear and replacing them can be more costly than replacing exterior surfaces.
For repairing uneven or worn interior concrete floors, contractors can use a self-leveling floor resurfacer. Owens notes that such products are effective at raising low areas that are up to 1½ inches deep. He explains its application: “Start with a good clean slab, apply a bonding adhesive and allow it to dry. Pour the resurfacer in 1-foot strips. It then will melt together raising the low areas. Our fast-set self-leveling resurfacer will dry within two to four hours compared to 24 hours for its normal set counterpart. Both should be allowed to cure seven days before installing tile or carpet.”
Owens says the product can be used outside if the environment is controlled to protect the floor from wind, excessive heat and other natural elements.
Many of the same products used to repair horizontal surfaces can also be effective with vertical surfaces, such as exterior retaining walls and interior load-bearing walls.
“Replacing some basic vertical surfaces, especially load-bearing walls, can become very expensive,” Rizzo says. “Coatings that improve aesthetics and also give durability to the surface become a real time and money saver for the property owner.”
There’s no question that contractors can offer customers more repair options than ever before. Although the makeup of concrete hasn’t changed dramatically over the last 20 or so years, repair products have. Polymers help create a strong bond between new and old concrete, acrylics add strength, and attractive finishes disguise patching and other repairs. Concrete surfaces can not only be filled in, leveled, livened up, and strengthened without expending the time and money to replace old concrete, surface treatment can actually make them look as good if not better than new.
Yes, as the above manufacturers point out, there are occasions when replacement is the only option. Short of that, when time, money, aesthetics and sustainability are priorities, repair becomes a very attractive alternative.
Based in Neenah, Wis., Rod Dickens is a freelance writer specializing in the construction industry.