Start by removing any visible peeling and flaking and use a solvent based stripper such as Xylene to remove the previous sealer. (If concrete was dyed or stained, using Xylene can damage or change the color of the concrete.) Pressure wash the surface and allow concrete to completely dry.
In most cases, using a chemical stripper is the easiest and most cost effective way to remove an old sealer from concrete. Chemical strippers are made from alkaline chemicals that dissolves and deconstructs the sealer film, allowing for easy removal from your surface.
For some reason, this idea that vinegar will remove concrete sealer has become one of the more pervasive myths about concrete, and it is just that: a myth. That's because almost all concrete sealants are made to be resistant to acid, which vinegar is. As if that wasn't enough, vinegar can actually damage concrete.
The easiest way to remove a concrete sealer is to begin by acid etching the surface of the concrete with muriatic acid. This process can be dangerous if you are unfamiliar with it; however, it is well within the ability of any ordinary homeowner, as long as the proper care is taken.
Unfortunately, muriatic acid is often used because it's less expensive than professional products. However, using muriatic acid is not a wise idea because it can actually cause damage to the concrete surface and to people, pets and plants.
Sealers can be removed with mechanical means such as sandblasting or grinding. But for many contractors, it's a last resort. It destroys the original surface, exposes the aggregate and is a mess to clean up.
A strong enough power washer will blast most types of sealer off of concrete with ease. The trick is to make sure to pressure wash the entire surface area. For more sturdy sealers, it may take a few passes with the pressure washer to get it completely removed.
Over time, it can destroy concrete as the acid weakens its structure. This will cause scaling, pitting, peeling, and cracking. If the acid wash gets into the soil, it will evaporate on the surface but remain beneath the surface (just like it does with concrete).
Scrub the acid solution: Once the solution is applied, lightly scrub it into the concrete with a push broom or long handled scrub brush. This helps to create a uniform etch of the concrete. Let the solution sit from 2 – 15 minutes while it continues to fizz and bubble.
Soda blasting, a less aggressive mechanical method, has become more widely used in recent years to remove sealers and coatings successfully. Soda blasting utilizes special high-pressure blasting equipment with commercial-grade baking soda granules as the blasting medium.
The standard solvent bath process involves spraying store-bought xylene or acetone across the problem area. (As a side note, I do not recommend acetone, as it dries too quickly to be effective.) You wait a few minutes to allow the solvent to liquefy the sealer, then wipe or roll the area to eliminate the problem.
A simple floor stripper or paint and epoxy remover is something you can use to remove asphalt sealer. A caveat, though: you can only use paint and epoxy remover on concrete, metal, wood, and masonry. Do not use this on vehicles and walls as the product could strip the clear coat or paint off.
When the sealer is applied too heavily, the air displaced through the surface can't escape, and it forms a bubble in the sealer surface. Bubbling of a sealer can also occur if application is done in hot weather, or if the concrete is in direct sun.
Another option is to sand off the sealant either by hand with sandpaper or by using an electric sander. Be sure that the sealant has dried first before sanding. If you have a pressure washer, another option is to use a sandblast kit to sandblast the concrete and remove the sealant.
Removing old sealers from natural stone is important if you are looking to renovate the natural stone tiles. LTP Solvex is a high performance stripper designed to remove most types of sealer from Travertine, Slate, Terracotta, Quarry.
Any concrete that is not properly neutralized will begin decomposing immediately. It may take time for the damage to reach the surface where you can see it, but it is happening and is usually irrepairable.
Like any strong acid, muriatic acid can irritate your skin (prolonged exposure can even cause burns). Gloves will help you avoid direct contact. If you do get muriatic acid on your skin, wash the area with clean water right away (it's a good idea to keep a garden hose or a bucket of clean water nearby).
Muriatic acid may damage concrete surfaces, so be careful when pouring it on sidewalks or driveways; new concrete typically does not need to be cleaned at all before applying staining agents. If you do pour some on these surfaces, rinse off with lots of water as soon as possible.
Muriatic acid is strong enough to etch concrete, but it can also cause severe injury and/or damage property when used improperly. Always wear protective clothing, rubber gloves, boots and goggles or a face shield when handling acid. Avoid breathing acid vapors.
Keep a supply of baking soda or garden lime nearby in case you need to quickly neutralize muriatic acid. While sprinkling these substances full-strength will work, the best plan is to mix ½ cup of baking soda and a quart of water in a sealed spray bottle and keep it nearby.
Muriatic acid can work wonders on filthy concrete. However, it shouldn't be used on penetrating sealers since it can damage these finishes. It might also damage some acrylic sealers, so test a small area if you're not sure.
Acrylic Concrete Sealers: Acrylic sealers last 1-3 years before they need to be re-coated. Epoxy Coatings: Epoxy coatings last 5-10 years before they need to be re-coated. Urethane Coatings: Urethane coatings last 5-10 years before they need to be re-coated.