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What Is Concrete Floor Sealer?

Nov 13, 2020

Concrete floor sealers are applied on top of the concrete surface to protect them from abrasion, corrosion, weathering and staining. There are many types of concrete floor sealer available in the market. 

They can be classified into 2 main categories: film formation sealers and penetrating sealers. 

Film formation sealers are thin layer of impermeable film formed after the application. The thin film acts as a layer of protective barrier to prevent dirt pick up and direct damages on the concrete surface. Film formation sealers are generally glossy. Special additives can be added to lower the gloss effect and provide a low gloss finish or matte finish. Film formation sealers enhance the aesthetics of the concrete surface by giving it a wet look finish. The colour of the concrete floor will be darkened and enhanced. Most film forming sealers may require a recoat as this layers are generally sacrificial layers. Recoating of the sealers will depend on the type of film forming sealers, wear and tear, type of traffic and type of exposures. 

On the other hand, penetrating sealer penetrates into the concrete through its pores. Unlike film formation sealer, penetrating sealer has no film formation on the concrete surface. Instead some penetrating sealer promotes chemical reaction between the sealer and concrete to form a denser concrete surface. 

You can find the following types of film formation sealers:
1. Solvent-based acrylic sealer
In solvent-based acrylic sealer, acrylic particles are suspended in a solvent typed liquid carrier. The solvent will evaporate after the sealer is applied on the concrete surface, leaving the solid acrylic particles to form a thin film. Application of solvent-based acrylic sealers enhances the colour of the concrete surface compared to water-based acrylic (see below) sealer. In general, they will darken the concrete surface and provide a wet-look effect, which most water-based acrylic sealer would not be able to impart. 

However, solvent-based acrylic sealers normally emit a strong vapour and pungent smell as they contain volatile organic compounds (VOC). Care must be taken, as these materials are flammable. Proper ventilation will be required when working with solvent based sealers. 

2. Water-based acrylic sealer
Unlike solvent-based acrylic sealer (see above), the acrylic particles are suspended in water instead of solvent based liquid. Due to this feature, the water-based acrylic sealer is environmentally friendlier. They do no emit pungent smell and harmful gases into the environment. This explains why most of the manufacturers claim that water-based acrylic sealer is a green, eco-friendly product. 

Another weakness of water-based acrylic sealers is that they don't function well at low temperature. They tend to freeze when the temperature hits around 10 degrees Celsius. Besides that, applicators are discouraged to apply the product when the surrounding temperature is too low or humidity is too high. You may end up with white patches or powdery finishing as the coalescing solvent evaporated before the water does. The solid acrylic particles could not make it to form a film before they are dried.

3. Polyurethane 
Polyurethane coating, also known as PU coating, are generally thicker compared to acrylic sealer. They are known for their excellent performance against abrasion, weathering, chemicals and staining. As with acrylic sealer, they are available in solvent-based and water-based. Identical to the solvent-based acrylic sealer, most solvent-based PU coatings have a high level of VOC. Thus extra care should be taken during the application to prevent any mishap. 

PU coatings can be used for indoor and outdoor applications. They are also suitable to be used in high trafficable areas (for example theme parks, car parks, car porch, etc.) due to their high abrasion resistivity. Some PU coatings could also be used for concrete countertops or pebble stones finishing. Glitters could be added to the mixture to have a sparkly finishing. 

4. Epoxy
Epoxy coatings are very similar to PU coatings. They too can be categorized into solvent-based and water-based. They have thick film formation. They could be coloured by pigments and glitters. They have good waterproofing properties and excellent performance against chemicals and staining. Additionally, application on kitchen countertops is very common. 

So, how to differentiate between a polyurethane (PU) and epoxy coating?

Traditionally, PU has a higher crosslink density compared to epoxy. Thus, PU coatings have better flexibility and elasticity as compared to epoxy coatings. Meanwhile, epoxy coatings are harder and more brittle than PU coatings. Besides, PU coatings tend to have better abrasion resistance than epoxy coatings. This explains why PU coatings are a more popular choice for heavy traffic areas, such as multi-storey car parks. Epoxy coatings are sensitive to UV, and are better suited for indoor applications. Epoxy coatings will turn yellow when exposed to UV 

Apart from that, epoxy coating that has good solvent and abrasion resistance is a popular choice in the industrial and healthcare industry. Such properties are very important in these industries as the coating will likely be experiencing heavy wear and tear, chemical spillage, as well as daily cleaning and scrubbing.

Other than the conventional pigments and glitters, flake could be added to epoxy coatings. Different designs with the flake can be customized according to clients' request too. Anti-slip aggregate could also be used in the epoxy coatings to enhance the skid properties. 

You can find the following types of penetrating sealers:
1. Silicone sealer 
Silicone concrete sealer is one of the common penetrating sealers available in the market. The silicone sealer penetrates the substrate to build a protection layer against damp penetration. Unlike the film-forming sealers, the application of silicone sealer will not change the final appearance of the floor. They are known for their clear and matte finishing on the surface applied. Besides that, they are handy at shielding the floor and wall from weathering and staining. Silicone sealer could also be applied temporary on concrete walls to protect the wall from graffiti. The downside of silicone sealer is that it required resealing from time to time. 

2. Silicate sealer
A silicate sealer is also known as the concrete hardener or concrete densifier. When the silicates penetrate to the substrate to react with calcium hydroxide found in the concrete substrate, a chemical reaction will take place to form calcium silicate hydrate (C-S-H). C-S-H is the same product that is obtained when cement is hydrated. The freshly formed C-S-H will be settling in the pores and voids, which resulted in a denser concrete surface. 

The silicate sealers that are commonly available in the market are sodium, potassium, magnesium, and lithium silicates. Sodium silicate has a bigger molecular structure among them. Thus, it is uneasy for the silicate to penetrate deep into the pores of the substrate. Lithium silicates are widely preferred as it has a smaller molecular structure. Hence, it can penetrate well into the pores and voids of denser concrete substrates.

Similar to the silicone sealer, the application of silicate sealers would not change the final appearance of the finishing. 

3. Silane-Siloxane sealer
Identical to the penetrating sealers listed on top, silane-siloxane sealers too penetrate deep into the concrete substrate. The chemical reaction then takes place, where a hydrophobic layer is found within the pores and voids. By increasing the surface density and minimizing the amount of liquid penetrating the surface, the water beading effect could be observed after the application. 

Unlike the other penetrating sealers, some silane-siloxane sealers will darken the concrete surface after application, thus providing a wet look appearance. This is because some of the silane-siloxane sealers are normally applied for 2 coats; some could go up to 3 coats. 

If you are looking for a concrete floor sealer for your home or job site, feel free to contact us for more information. 

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