What is Sealcoating Made of? A Quick Explanation

What is Sealcoating Made of? A Quick Explanation

Regardless of how well-installed your asphalt pavement is, it’s still vulnerable to the elements. That means it is prone to cracking and holes. So, you shouldn’t be surprised if your asphalt starts to fade a few months after installation.

Now, this is where the need for asphalt sealcoating comes in. An asphalt sealcoat is a blend of liquids and other small particles like sand, and it acts as a protective layer to asphalt paved surfaces. Sealcoating helps to protect asphalt from external elements like water, chemical spills, UV rays, and ice, which can damage the surface.

Therefore, sealcoating your asphalt surface reduces the risk of cracks and holes forming on the surface. Besides, sealcoating an asphalt pavement gives it an impressive deep black appearance, while preventing it from becoming slippery.

The main ingredients of sealcoat

The following are the major ingredients used to produce asphalt sealcoating.

Coal tar

A refined coal tar-based asphalt sealer is an emulsion that consists of the following three ingredients:

Coal tar – this is a refined type of byproduct known as coke oven tar. Typically, coal tar is a residue that’s left after distilling oils for use in consumer and industrial manufacturing. This product is refined and then separated into 12 grades of thickness–and each is used in different industries like the steel and aluminum industries. The thickest grade is RT-12, and it’s used to produce coal tar sealers.
Emulsifying agent – this is also referred to as a surfactant. The agent is a soap-like, water-soluble substance, which is made of two molecules: ionic head and hydrocarbon tail. Now, these two molecules cover the coal tar particles, thus giving them an electric charge. This, in turn, causes them to repulse each other and this is what makes them remain suspended in water.
Additives – generally, a coal tar sealant is mixed with clay, sand, and polymer additives. This improves its durability and makes it easier to apply the sealer. Since coal tar sealers are governed and produced to meet specific federal specifications, professionals use a blend of these additives to produce different grades of asphalt sealer.

Asphalt emulsion

Asphalt-based sealers primarily consist of the following three ingredients:

Asphalt – this is a refined type of crude petroleum oil. It constitutes 50 – 70% of a typical asphalt emulsion. Generally, asphalt has different production methods, unlike coal tar. That means, different companies produce asphalt with different compositions, and this can affect the sealant’s viscosity. Furthermore, because asphalt is a petroleum-based product, it resembles petroleum-based automotive fluids and fuels. That means asphalt isn’t resistant to fuel.
Emulsifying agent – generally, the emulsifying agents used in asphalt-based sealers play a similar role as the agents used in coal-tar emulsions. However, they do differ in terms of chemical properties and compositional differences of the asphalt used. Please note that coal tar is a standardized product, while asphalt is a variable product. All in all, the emulsifying agents are used for chemical compatibility, which creates a stable emulsion.
Additives – there are two types of additives used when making asphalt emulsions. These additives are polymer and non-polymer sealants. These additives can either be waterborne vinyl or waterborne acrylic resin. Now, the local temperature and environment gradients determine the kind of additives required for the final mixture. Please note that mixing the additives requires a lot of precaution. However, because asphalt-based sealers aren’t standardized, they might contain certain properties that are not compatible with some additives, and they can affect the functionality of the sealer.

Emulsion additives

Both coal tar and asphalt emulsions are sold either in concentrate or ready-to-use forms. The ready-to-use forms come pre-mixed, with water added to create a thick slurry. On the other hand, concentrate forms are mostly used in construction applications and they require the addition of water and other additives to get the final result.

The following are the most common additives used in sealant mix together with their benefits:

Sealing additives – typically, both polymers and non-polymer sealers are added to asphalt emulsions to serve as an active sealing ingredient. However, they can also be added to a coal tar emulsion. Sealing additives add durability, elasticity, and strength to sealants, and are usually added as emulsions to make the mixing process easier.
Aggregates – aggregate, boiler slag, and sand are a common addition to the sealant. They are added at a rate of 2 – 5 pounds for every gallon of concentrated sealer. Any form of aggregate helps to improve skid resistance, dry time, and wearability, in addition to filling any defects on the surface and creating a uniform texture.
Water – this is a simple additive that plays an important role in a sealant mix. Water ensures proper flow and leveling of the sealant. Generally, asphalt emulsion sealers can be diluted up to 25%, while coal tar emulsion sealers require more water.

The importance of sand in sealcoating

Most people think that sand manufacturers add sand to sealcoating to reduce costs or to add the quantity of sealcoating. However, that’s not the case. According to the sealcoating contractors at ABC Paving, sand plays an essential role in improving the durability of the sealcoat, in addition to enhancing traction to the surface. Besides, sand helps to conceal minor imperfections on the pavement. Typically, manufacturers use high-quality silica sand, which has uniform particles, rather than the normal sand.