How you reseal stamped concrete will depend on the type of concrete sealer currently down, and what you want the stamped concrete to look like once sealed.
Best Practice Tips For Reapplying A Concrete Sealer On Stamped Concrete
Water Based Acrylic Sealer: If the stamped concrete is currently sealed with a water based acrylic sealer, it is best practice to maintain the surface by reapplying with only a water-based concrete sealer. You can't apply a solvent based acrylic sealer over a water based acrylic sealer because the solvents will chemically react and attack the water based product, resulting in coating failure. The only way a solvent based acrylic sealer can be applied to stamped concrete previously sealed with a water based acrylic is if the water based acrylic sealer has been completely removed. Water based acrylics will provide a low to high gloss finish without enhancing or darkening the color of the concrete.
Solvent Based Acrylic Sealer: If the stamped concrete is currently sealed with a solvent based acrylic sealer, it is best practice to maintain the surface by reapplying with only a solvent-based concrete sealer. Normally there is no other prep required other than making sure the surface is clean and dry. Solvent based acrylics will provide a low to high gloss finish, and will darken the stamped concrete to make it look wet.
Penetrating Sealer: If you previously applied a penetrating sealer such as a Silane-Siloxane water repellent, and you want to reseal it with a water repellent sealer, you can often times reseal it with a solvent based Silane-Siloxane water repellent so long as the stamped concrete no longer beads. Water based water repellents will run into issues with penetrating, but solvent based water repellents can usually penetrate without issue. Water repellent sealers are typically reapplied every 7-10 years.
- SX5000: Water Repellent Sealer
Unsure: If you aren't sure what your stamped concrete is currently sealed with, you want to run a quick Xylene/Xylol test. Find an area where the sealer is still visible and mark off a 1 FT X 1 FT area. Keeping the roller wet with Xylene/Xylol, roll over the area until it gets tacky. If the surface gets sticky/tacky, leave it to dry for 24 hours. If nothing happens after a couple of minutes, leave the area to dry 24 hours. The next day, if the sealer looks the same or better, you most likely have a solvent based acrylic sealer down. If the area looks worse, has turned white, or has delaminated, you most likely have a water based acrylic sealer down. If you can no longer see the sealer to do the Xylene test, and it is has been at least 5 years since being sealed, this test may not be necessary. The old sealer is most likely gone and a simply pressure washing is all that is needed. If the old sealer is gone, you are normally free to recoat with any type of sealer you'd like.
Regardless of what the stamped concrete is currently sealed with, or what it will be resealed with, it is always suggest to apply the new sealer to a test area first to verify finish, compatability, and adhesion.