The cause of “spalling” or “scaling” concrete is simple. Concrete is porous and soaks up a lot of water. When that water freezes, it expands and breaks up the concrete surface. Prevention is pretty simple too: Apply a sealer to reduce water penetration.
There are many types of sealers. For most sidewalks and driveways, the best choice is an acrylic sealer. Acrylics work by forming a clear coating on concrete. The coating is easy to apply with a roller or sprayer and will last two to five years, depending on weather and traffic. Some products give concrete a glossy “wet” look, while others leave a duller matte finish.
You’ll pay $20 to $40 per gallon, and cost is often a clue to quality. Also check the label; higher quality acrylics are “nonyellowing” and require new concrete to be fully cured (14 to 28 days, for example). Acrylics cover 100 to 200 sq. ft., depending on the porosity of the concrete.
Home centers carry acrylic sealer (in the masonry aisle), though some sealers don’t say “acrylic” on the label. A few common brands are Quikrete High Gloss Sealer, Quikrete Acrylic Cure & Seal, Rust-Oleum Concrete Sealer and Sikagard Sealer.
Acrylic coatings can make concrete slippery. So if you have smooth steps or walkways, there’s an alternative you should know about: Penetrating sealers such as “silane” and “siloxane” create a barrier within the concrete rather than on the surface. Available only at specialty concrete suppliers, they usually cost more and degrade faster than acrylic.
Concrete soaks up water, which freezes and busts up the surface.
Apply a sealer to lock out water.
The concrete looks just like it did before, but water beads up on the surface and doesn’t soak in.