Exposed aggregate is a beautiful finish for a driveway, but installation isn’t complete until the aggregate has been sealed. Proper sealing and resealing will ensure the driveway lasts not just a few years, but for decades. Even sealed aggregate is vulnerable to intense weather, UV rays, and freezing and thawing, so it may need to be resealed eventually. The question is, how often should an exposed aggregate driveway be sealed?
The answer depends on what kind of sealer is used. While some sealers can last for ten years or more, others ensure results for only one to five years. A sealer that costs more may represent a better long-term investment since it will not need to be reapplied as quickly. And finally, even the best sealer may not last long if the product is hastily or unevenly applied. Be sure to follow the directions for whichever sealer is used to ensure the longest lifespan for your aggregate driveway.
Silicate concrete sealers are the longest-lasting, with one application potentially lasting a lifetime. This sealer represents an excellent investment for long term driveway protection. Silicate is a penetrating, densifying sealer. It penetrates the pores of the concrete and effects a chemical change. Ultimately, the sealer strengthens the aggregate, protecting it not only from stains and water damage but from abrasions and warping as well. Silicate concrete sealers can cost a bit more, but they create a permanent finish and are virtually maintenance-free.
The next longest lasting options are silane siloxane water repellent sealers and siliconate water repellent sealers. These can each last from seven to ten years. As water repellent sealers, these protect aggregate driveways from water damage caused by snow, ice, mold, and mildew. There are a few key differences between these two options. Siloxane can be applied to light and dark surfaces without issue. Siliconate, on the other hand, can stain. If over-applied, siliconate sealer can turn the aggregate white. Due to the color issue, it cannot be applied to dark surfaces.
Less long-lasting products include epoxy and urethane sealers. Epoxy and urethane coatings require reapplication every five to ten years. They work by coating the exterior pores of the concrete, protecting the concrete from liquids including water, ice, and even industrial fluids like oils. Epoxy and urethane coatings may bubble when applied, so be sure to follow the directions for a professional-looking result. They can come in a variety of colors, as well as the traditional clear finish.
The shortest lasting products are acrylic concrete sealers, which will need to be reapplied every one to five years. The acrylic sealer works by creating a film over the concrete. It covers the aggregate with a thin waterproof barrier. Acrylic concrete sealers come in water-based and solvent-based formulas. Solvent-based sealers emit vapors and can consequently have a strong, offensive odor. The vapor can be hazardous to health if inhaled. Additionally, the fumes can ignite, so safety precautions should be followed carefully. Solvent-based acrylic sealers have a glossy finish but may darken the concrete as they dry. On the other hand, water-based acrylic concrete sealers are non-flammable and do not emit vapors. They will not darken the concrete, but the finish will also not be as glossy as the solvent-based sealer.
And finally, even the best sealer may not last long if the product is hastily or unevenly applied. Be sure to follow the directions for whichever sealer is used to ensure the longest lifespan for your aggregate driveway.