A-Tech Concrete Sealer-Silane & Siloxane Concrete Water Repellent

December 5, 2012

Concrete water repellents are used to protect concrete areas such as driveways, patios and sidewalks from water penetration. They need to be able to stop water from getting into concrete. But most importantly, it must be able to also let water vapor escape out of it.

There are several types of water repellents available, some of them at your local home improvement center. Unfortunately these readily available water repellents are unable to let water vapor escape and do not penetrate into the concrete. They contain acrylic, paraffin or silicone. Professional contractors use a type of penetrating water repellent made of a silane/siloxane solution which stops water and allows water vapor to escape. They are available from several manufacturers or at professional concrete contractor supply warehouses. While silane/siloxanes are not at the big box stores they are very easy to use

Penetrating Sealers vs. Surface Sealer

Sealers made of a silane/siloxane combination penetrate below the surface of the concrete. They leave no surface film and are virtually invisible to the eye. Because they penetrate below the surface they last a lot longer than surface sealers which can be worn away by foot and vehicle traffic. Silane/siloxane water repellents do not have any gloss or sheen to them. The substrate's natural look, texture and traction qualities will remain the same. Surface sealers work by remaining on top of the concrete and physically sealing the pores of the concrete. They eventually wear away from traffic and use. Also the sheen can become cloudy.

How Silane/Siloxane Water Repellents Work

Silane/siloxane water repellents work by getting into the microscopic pores of the concrete. They bond to the sides of the pores of the concrete and because they are hydrophobic, water cannot enter. Most importantly the pores remain open. This allows any water vapor that is in the concrete from the soil below or the inside of a building to get out. The water vapor will naturally evaporate out. Silane/siloxane water repellents are called a "breathable" sealer. Liquid water stays out but water vapor can evaporate. The ability to breathe helps prevent spalling and flaking of the concrete. If water were to be trapped inside the concrete and then freeze, the freeezing causes the water to expand and that causes the concrete to flake and spall.

Prevent Spalling, Flaking and De-icing Salt Damage

One of the causes of spalling and flaking is water getting inside the concrete. This water expands when it freezes. The expansion of the ice breaks the bond of the top layers of concrete which is called flaking. Spalling is caused by the reinforcing steel inside the concrete rusting and expanding. This expansion of the steel from rust also causes the concrete to delaminate. De-icing salts can get into unprotected concrete and cause the reinforcing steel to rapidly corrode. By applying a silane/siloxane water repellent much less de-icing salt can get into the concrete.

Silane/Siloxane Advantages

  1. Concrete becomes water repellent
  2. Silane/Siloxane penetrates below the surface
  3. Water vapor escapes
  4. De-icing salt protection
  5. Concrete looks the same as untreated

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