How To Remove Concrete Sealer (Solvent Based & Water Based) Tips and Techniques
Concrete is one of the most popular building materials used in commercial and residential construction. It is therefore important to provide as much protection as possible to concrete in order for it to keep its appearance as well as its strength. That protection is provided with a concrete sealer.
Concrete sealers do break down over time and will need to be replaced to offer the best protection. This will require removing the old sealer and replacing it with a new layer of protection.
How To Tell If Concrete Is Sealed
If you are unsure if the concrete in question has a sealer on it, you can perform a simple test or two to determine if it does.
Water drop test
You can apply small drops of water on various areas of the concrete to detect the presence of a sealer. If the water discolors the concrete and absorbs into the surface, the concrete likely lacks a concrete sealing barrier. If, however, the water beads on the surface and does not absorb into the surface it is probable that a sealer is present.
Muriatic acid test
Some concrete finishes are smooth and will naturally lack a porous surface for water to penetrate, making the water test of little use. In this case, applying muriatic acid will indicate the presence of a concrete sealer.
A four to one mix of water and muriatic acid will interact with the lime in concrete, generating bubbles or fizzing if the surface is bare. If a sealer is present, the mix will not generate a reaction.
How To Determine What Type Of Concrete Sealer Was Used
If a concrete sealer has been used, your next step will be to determine if it is a water-based or chemical-based product. This is an important step to consider, as a water-based product cannot be applied over a chemical-based product and a chemical-based sealer cannot be applied over a water-based material.
You can apply a small amount of Xylene to an area of your concrete. After letting it sit for 20-seconds, remove the Xylene and touch the concrete. Chemical-based sealers will gum up and become sticky, while water-based products will not.
How To Remove Concrete Sealer
One method of sealer removal is to strip the product through a mechanical means. Thin layers of concrete sealer, especially water-based products, can be stripped by using a pressure washer. The high-pressure water can break the coating free from the concrete surface and the water will then wash the debris away.
Specialized Tools Required
In most cases, however, mechanical removal will require you to grind or sand the coating off of the surface. This will require you to rent or purchase equipment that can be used to bead blast, shot blast, or scarify the concrete.
Noisy And Dirty
These procedures will generate a lot of dust as well as noise as the equipment is used. That will require that you also purchase extra protection for your ears and lungs. This process will also require extra labor when operating the equipment and could also create extra work if the concrete surface is damaged during the stripping process.
The Other Option...Chemical Removal
Due to the extra costs and work involved with mechanical removal, many homeowners will instead use chemicals to strip away sealer or hire a professional to mechanically strip away the protective coating.
Chemical removal (My Preferred Method)
The more common process employed by homeowners is to use a chemical product to remove the protective barrier. These chemicals interact with the concrete sealer by breaking the material down into a sludge that can then be cleaned off of the surface. If you’re working on decorative concrete, this removal method is preferred as it will not damage the surface below the protective layer.
Keep The Chemicals Active
The trick to using chemical strippers effectively is to keep them active. These solvents will only work if they kept moist, as they will deactivate when dry. Look for a product that is gel-based, as these tend to remain active longer than liquid-type products that will evaporate quickly.
A Note About Concrete Surfaces
A flat slab of concrete will be easier to work on than a piece of concrete with grooves or decorative textures. Uneven concrete surfaces will often require several applications of chemical removers in order to pull the sealant from the depressed areas. Extra time will be required to remove the sludge once the protective barrier is broken down as well.
Applying A Chemical Stripper
Use Protective Gear
To begin with, you will want to make sure that you have the proper protective gear. These chemicals can be harsh, so make sure that you follow the manufacturer's suggestions and avoid making contact with your skin or eyes.
Also, keep in mind that you need to provide plenty of ventilation in the work area. This is especially important if the concrete section is indoors, as a lack of airflow can be harmful and may require your house or garage be evacuated for an extended period as the vapors dissipate. This applies to "eco-friendly" products as well as traditional compounds.
Follow The Manufacturer’s Instructions Exactly
Follow the directions listed on the product exactly. This will help to prevent damage to the concrete surface below the sealer and keep you safe while you work.
Pro Tip!: A trick that you might consider when working with the product is to cover the work area with a damp cotton bed sheet. This will help to keep the chemicals moist and active, allowing them the proper amount of time to be effective.
Remove The Sludge With A Scraper or Trowel
Once the stripper has sat for the suggested amount of time, you can remove the sludge using a scraper or trowel. Once the surface is dry, you can determine if extra applications are necessary. If another coat of stripper is required, follow the same steps you used during the first application.
Clean or Pressure Wash The Concrete
Once the concrete sealer has been removed, you should clean the surface with water to remove materials that are still present in pores or depressions in the concrete surface. Many homeowners will use a pressure washer at this stage to remove left-over debris. Your concrete should now be ready for an application of new sealer to keep it protected from for years to come!