Should I use a Concrete Densifier?

Should I use a concrete densifier to seal my concrete?

In short, yes, you should use a concrete densifier to seal your concrete. Densifiers can’t be applied to just any concrete surface. Concrete densifiers can only be applied to concrete if the concrete has either never been sealed before, or is currently completely free of old concrete sealers and coatings. Densifiers need to penetrate through the surface of the concrete in order to chemically react. If they are unable to penetrate and reach the free lime and calcium in the concrete pores then they either won’t react, or will react on the surface.

Densifiers can be used on both interior and exterior concrete surfaces. They increase the surface strength of the concrete and reduce the size of the pores by filling them in with a crystalline barrier. There are many benefits of using a densifier, but the most common are:

  • Increase surface strength to reduce surface dusting
  • Increase surface strength in order to increase resistance to surface abrasion
  • Increase resistance to abrasion caused by road and de-icing salts
  • Strengthen weak or deteriorating concrete
  • Reduce the movement of sub-surface water and moisture through the pores

Densifiers should only be used on concrete that is going to be left unsealed, concrete that is going to be sealed with a water repellent sealer, or concrete that is going to be polished. Densifiers should not be used on concrete that is going to be sealed with an acrylic sealer, epoxy coating, or urethane coating unless it has been approved by the manufacturer of the coating. Coatings use the pores of the concrete to bond so when pore size is reduce from a densifier, the coating may experience issues with bonding.

Common surfaces where densifiers are used:

  • Basement walls and floors
  • Garage floors
  • Shop and warehouse floors
  • Concrete driveways, walkways, and patios
  • Concrete pool decks

Densifiers should not be used to seal brick, pavers, stone, slate, or flagstone, unless. If it is suggested by a manufacturer you should work closely with a technician to make sure all instructions are followed. These types of surfaces are very porous, and some not porous at all. Some of them contain little to no calcium, and some of them have an over abundant supply. These surfaces have been found to cause a chemical reaction on the surface and when that happens, little white crystals form. These crystals, which normally form in the pores, are very hard, and in many cases impossible, to remove. Densifiers should only be used on concrete and in accordance with the manufacturer’s instructions.

Densifiers offer many benefits relating to increasing density and therefore strength, but there are many things a densifier can’t do:

  1. Densifiers can’t repel water. Densifiers are very different from water repellent sealers. Densifiers increase the strength of the concrete, but they don’t stop water absorption through the surface. If water is spilled on a surface sealed with a densifier, the concrete will absorb the water. Water repellents fill in the pores of the concrete with a hydrophobic, or water repellent, barrier. When water is spilled on the surface of concrete sealed with a water repellent sealer, the water will bead off the surface and the surface will look dry, even when wet. If you want a densifier and a water repellent, put down the densifier first and then wait at least a week before applying a water repellent sealer.
  2. Densifiers can’t stop Radon. Densifiers are breathable sealers and Radon is a gas. Radon will be able to move through sealed concrete just as easily as it will be able to move through unsealed concrete. While densifiers reduce the size of the pores, they only reduce pore size on the surface layer. Even if a densifier penetrates six inches, you won’t get a solid six inch barrier. If any Radon is reduced, it will be by a barely measurable difference. The best way to reduce Radon, or stop it, is to install a Radon mitigation system that vents Radon out of the basement. If you have any questions about Radon, contact the EPA, or a Radon mitigation specialist.
  3. Densifiers don’t change the look or color of the concrete, and they do not leave behind a film or coating. They work entirely below the surface. The concrete surface will look exactly as it did before being sealed.

Now that you are aware of the benefits of using a densifier, you need to make sure you choose the best concrete densifier for your application.

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