How do I reseal stamped concrete?
Ok, I get it, your stamped concrete is looking a little faded, blotchy, or even kind of whitish on the surface.
And you want to restore it to its original look when the concrete was first sealed, right?
In theory, resealing your stamped concrete should be quite easy, but if you're not careful, resealing it might make it look worse.
Does your sealer look like this?
Concrete sealers are designed to be applied very thin.
The manufacturer specifies on the label how many square feet per gallon of coverage. If they specify 300 square feet per gallon then that's what you should do.
If you think applying it at 200 square feet per gallon is better because it's a litte thicker, you're wrong.
Most sealers used for exterior stamped concrete are solvent or water based acrylic sealers. They are designed to allow moisture vapor to pass through them.
If you apply them too thick, moisture will get trapped on the surface of the concrete and under the layer of sealer causing "blushing" or whitish looking sealer.
Back to the question above, if you already have blushed (whitish) looking sealer that looks like a thick plastic coating, kind of peeling and flaking off, then applying a new coating of sealer over it will eventually trap more moisture and make the concrete look worse.
So this begs the question.
Well the answer to that is yes.
But we just don't want to make it look worse.
If you're like me, you like your stamped concrete looking new, clean, and either shiny or with more of a matte finish.
There's just some things we have to do before we re-seal your stamped concrete driveway, patio or pool deck.
Ok, first thing is to clean the concrete. I like to use a pressure washer with a cone tip. Keep the tip between 12 - 18 inches away from the surface of the concrete or you could leave lines from the pressured water on the concrete.
A 3000 psi pressure washer is all you'll need.
You're not trying to remove all the original concrete sealer. You just want to clean any dirt, pollon, and debris off the surface. You'll probably remove some loose, flaking areas of sealer but that's good to.
If you need to scrub the surface, you can use a stiff bristle broom and Dawn dish detergent or Simple Green mixed with water in a 5 gallon bucket. Just rinse really good so no residue remains after it dries out.
When you're done cleaning and washing the concrete it's very important you let it dry out. Wait at least 24 hours, 48 would be better. Even though the concrete looks dry on the surface, there's still a lot of moisture internally.
Most of the time, if there are any problems with old sealers, it's from solvent based sealers.
Water-based concrete sealers mostly "soak into" the concrete and don't leave much of a film on the surface. The concrete looks pretty much the same after sealing with a water based sealer as it did before the sealer was applied.
A lot less goes wrong with water based sealers but, in my opinion, they just don't give stamped concrete that "wow" look after its been sealed.
So, the failing or worn solvent based sealer has to be addressed but that doesn't mean you have to strip it off. Stripping old solvent based sealer is
messy and can be expensive if you have a lot to do.
In some cases it may be necessary, but most of the time it's not.
All you have to do to re-seal is make sure the new sealer has good adhesion to the old sealer.
How do you do that?
Don't think of it as applying a new coating over the old one. Think of it as mixing the new sealer into the old sealer. The new sealer must mix with
the old in order to release trapped moisture (those white areas) and reactivate the previously applied sealer.
Reactivating the old sealer will melt the ugly, flaky, and blushing areas all at once, releasing any moisture and making it look like new again.
The reactivating process requires a little more than just a pump up sprayer application. You are going to have to agitate the sealer as you apply it.
By agitating, I mean use a chemical resistant push broom and lightly broom over the newly sealed area. Just once back and forth may be enough.
It would work best if someone was spraying the sealer while someone else was agitating (brooming) a few seconds behind the sprayer.
Solvent based sealers usually dry very fast, so you won't have much time to agitate.
It's best to do the worse looking areas first, let them dry and then reseal the rest of the stamped concrete. Back-brooming the sealer will also keep you from getting any puddles. Puddled areas of new sealer will be too thick and could trap moisture.
Whenever I seal or reseal stamped concrete, I like to go very thin with the first coat. I might spray it on as thin as 500 sq. ft. per gallon.
It's so thin, it looks like I'm missing some areas.
The goal is to use as little as necessary to get the job done. Less problems that way.
This first coat usually drys in 20 - 30 minutes. If I think I need a second coat I'll wait until the first is completely tack free and spray on another
one at 500 sq. ft. per gallon.
TIP: To clear up whitened, cracked, and hazy looking concrete sealer sometimes it's better to try and re-melt the existing acrylic solvent based sealer with an application of xylene (xylol).
Xylene is a strong solvent that re-wets acrylic solvent based concrete sealers making them look new again.
Applying xylene by using a pump-up sprayer, roller, or brush rejuvenates the existing old sealer to its original appearance. By trying this method
first, you may get the original sealer to look smooth, shiney and clear without adding another coating of sealer.
What xylene won't do is seal any areas where the old sealer has completely peeled, flaked, or worn off. You might try a xylene application first, wait a few hours for that to dry, then reseal everything with a very light coat of new sealer.
If you view the concrete at an angle and the surface has some sheen, it probably has some sealer on it.
Another way to test for existing sealer is after the concrete has been completely cleaned, place a few drops of water on it.
If the concrete immediately darkens, the sealer is gone. If the water beads up, even for a few seconds, there's still some sealer on or in the concrete.
If your stamped concrete is just dull looking with no white spots or flaking, then just a simple cleaning and re-seal should be enough to make it look like new again.
I have less problems sealing concrete later in the day when the temperature of the concrete is going down versus sealing in the morning when the sun is warming the concrete up.
If you seal in the morning, the concrete could have some moisture in it just from the dampness in the overnight air.
Ever seen that moisture (dew) on your grass in the morning.
Then as the sun warms up the concrete, the moisture will escape the concrete as vapor. If you seal the surface, the vapor could cause blisters, bubbles, and blushing.
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That's us Pumping a slab!