Concrete Sealing – Using Concrete Sealant To Protect And Preserve

Concrete sealing is an excellent way to protect exposed concrete from weathering and the ravages of time. Concrete is a low cost, durable and versatile building material, but it needs treatment to prevent damage from water and frost. Concrete is extremely porous, and water penetration critically weakens the structure by re-dissolving the dried alkaline lime. This gradually damages the integrity of the concrete by causing it to soften, crack and flake.

For concrete strengthened with steel reinforcing rods, mesh or fiber, water attacks and corrodes the steel, causing it to become rusty and compromising the integrity. Apart from the risk of mechanical and structural failure, this also stains the concrete, which is extremely unsightly where the concrete is exposed. Whilst it is possible to buy epoxy-coated, galvanized or stainless steel concrete reinforcing rods, they are expensive and most older structures incorporate raw and untreated steel.

In areas of the world with icy, bitter winters, freeze-thaw action is the prevalent cause of concrete damage, gradually eroding the surface and weakening the structural integrity. In this process, water collects and gathers in small cracks and fissures in the concrete and expands as it freezes and turns into ice. These cracks slowly widen, eventually causing it to chip and flake, exposing a fresh surface that once again comes under attack, in a never-ending cycle.

Due to the porosity of untreated concrete, any water-soluble substance will permeate into the pores of the material, staining it and leaving permanent discoloration. A rusty watering can or barbeque left on a concrete patio or driveway will stain it, and the discoloration penetrates too deeply for it to be removed by a portable pressure washer or cleaning chemicals. Water damage can also be a severe risk to health: Apart from uneven footing caused by chipping and flaking, green algae can coat the surface of the concrete, making the surface slick and treacherous.

Repairing and replacing damaged concrete is a laborious and expensive undertaking, incurring huge costs for materials and labor. Removing the old concrete is difficult, time-consuming and will always weaken the structure. Layering new concrete over old always leaves a weakness, however sound the preparation and, of course, the new concrete will be attacked by the elements making concrete repair an eternal task.

For large and important structures, such as road bridges, storm drains and water towers, rebuilding causes weeks and months of disruption, as well as costing a huge sum of money. In areas prone to winter ice and snow, road salt speeds up the process of erosion by allowing the melt water to penetrate the concrete and speed up the freeze-thaw process. Untreated concrete road bridges and drains need replacing frequently, at great expense.

The easiest way to protect exposed concrete from weathering and water damage is to use water or solvent based concrete sealing agents. These concrete sealants are relatively cheap, easy to apply, and form and effective barrier against the ravages of time and the elements.

There are two main types of sealant, ones that penetrate the concrete and concrete sealants that form a surface film. The non-penetrating concrete sealants are a little cheaper to buy, but this protective barrier will wear away over time, and is no use where the concrete sees heavy traffic, such as busy kitchens. For many applications, it is cost-effective to spend extra money and purchase penetrating sealant, which is much more resistant to physical damage.

Many concrete sealants act as a barrier to penetrating water, completely preventing any moisture from permeating through. This type is suitable if the concrete possesses an impermeable barrier or damp-proofing agent on the other side, completely sealing the concrete against water ingress. If there is no water-retardant barrier, water still seeps into the concrete from the other side, especially in floors, driveways or basements. This will damage the concrete chemically and the structure is still subject to freeze-thaw action. The best quality concrete sealants form a semi-permeable barrier, which allows water vapor to escape from the surface of the concrete whilst protecting the surface.

Acrylic Concrete Sealant

Acrylic concrete sealing is the cheapest option, forming a barrier on the surface of the concrete. Acrylic resins are easy to apply and add shine to the concrete, useful where aesthetics is a concern, such as with concrete countertops. The main disadvantage is that acrylic resins are soft and easily damage, lasting only between one and five years.

The film formed by acrylic sealants is completely impervious, so the concrete must be completely dry before the sealant is applied and it is not suitable for concrete that allows water to penetrate from the other side. Acrylic and epoxy concrete sealants have a shiny and polishable finish, although an anti-slip coating is required if they are used on floors, patios and paths.

Epoxy concrete sealers provide an exceptionally strong and resilient finish, and are perfect in areas that are subject to heavy use, such as driveways and factory floors. Epoxy concrete sealant is expensive to buy and is completely impervious, so the concrete must be completely dry before application to prevent trapped moisture from causing damage.

For this reason, epoxy concrete sealer is a poor option when the concrete is subject to water penetration from other directions. Finally, epoxy based sealants generate toxic and flammable fumes, so care must be taken during the application process.

Siliconate concrete sealants are expensive but penetrate deeply into the concrete, forming an excellent semi-permeable barrier. Siliconate concrete sealers are the best option for sealing rough concrete, such as driveways, paths and concrete blocks.

Silanes are the most expensive type and provide deep penetration and excellent protection. The expense means that silane based sealants are used upon fine finishes, such as concrete countertops and porous stone.

Silicones and siloxane based concrete sealers are penetrative, but they do not penetrate very deeply into the concrete. Because of this, they are subject to the same issues of wear and tear as film-forming sealants, so tend to be used upon concrete walls and supports, helped by the relatively low price.

Just to complicate matters, it is possible to apply concrete sealing that is a combination of many types, although they can be a little expensive. Often, contractors will apply silicate-based sealants, to provide lasting protection, and follow up with a coat of acrylic or epoxy, for appearance.

Finally, concrete sealants are available in a wide variety of colors, textures and shades, as well as in gloss and matt finishes. This is a matter of personal choice and budget, but concrete sealant can be beautiful as well as practical.