Slurry Seal vs. Seal Coat: What’s the Difference?

Asphalt is a highly durable paving material with a lifespan of roughly twenty years or more. Despite its inherent strength and stability, asphalt is susceptible to damage if not adequately protected. In fact, extensive water and UV exposure can cause the surface to oxidize, making it more prone to structural issues.

When it comes to repairing your commercial parking lot, it’s essential to know your sealing options and the differences between slurry seal and seal coat. While slurry and seal coat are preventative maintenance solutions that help your asphalt last longer, there are several key differences to be aware of.

While any professional contractor should be able to explain the advantages of both, this article will lay out some of the fundamental differences between a slurry seal and seal coat and the benefits of each to help you make the best decision for your property. Continue reading below to learn more and find out why South Central Sealing & Paving is Wichita’s number one choice for high-quality asphalt maintenance services.

The Differences Between Slurry Seal and Seal Coat

The two main components of any asphalt surface are crushed gravel aggregate and a sticky asphalt binder made from petroleum derivatives. When heated, the asphalt binder becomes semi-fluid, making it easier to spread. However, as the paving cures, the binder thickens, effectively locking the aggregate chunks into a stable matrix.

Even though asphalt binder continues to evolve, oxidation caused by environmental exposure weakens the binder, making it more prone to damage. As a result, the asphalt loses much of its water resistance resulting in cracks, potholes, raveling, and shoving beginning to show.

However, preventative maintenance solutions such as slurry seals and seal coat are designed to protect the asphalt by applying a protective layer of material to the surface. These solutions make the asphalt more waterproof and protect it from harmful environmental factors.

So, what’s the difference between slurry seal and seal coat? Let’s take a closer look.

What Is Seal Coat?

Seal coating is a preventive maintenance solution that involves applying a protective layer of material to an asphalt pavement surface to keep it waterproof and protect it against damage caused by weather, oxidation, and normal wear and tear.

Seal coat also keeps vehicle fluids from entering and damaging the pavement’s interior structure and improves the aesthetics of asphalt by restoring its lustrous black appearance. As a result, seal coat is one of the most commonly available asphalt-protection methods for commercial properties looking to revitalize their asphalt surfaces.

There are two common types of seal coat: those made from coal tar and those made from asphalt emulsion.

Most contractors prefer to use coal tar seal coat, as it produces more consistent results than seal coat produced from asphalt emulsion, which often varies. Although, the low cost and availability of asphalt emulsion seal coat are quickly making it the most popular selection. However, many manufacturers have started offering blended seal coat solutions containing varying proportions of coal tar and asphalt emulsion.

Seal coat can be applied by hand or with truck-mounted pressurized sprayers, depending on the size of the asphalt surface being treated. The surface must first be thoroughly cleaned to remove all traces of dirt, oil, and debris, as foreign substances will significantly reduce the seal coat’s ability to bind with the asphalt.

After applying seal coat, it should not be used for 24 to 48 hours, depending on environmental factors such as temperature and humidity. This waiting period allows water in the seal coat to evaporate, leaving a sealer film behind.

Curing time can range from several hours to several days, depending on environmental factors such as temperature and humidity. As a result, many contractors recommend applying seal coat during warmer, drier months for optimal curing rates and reapplying the solution every 2 to 3 years.

What Is Slurry Seal?

Slurry seal is a process of using asphalt emulsion, water, aggregate, mineral filler, and other additives to create a preventive maintenance solution that resurfaces an existing asphalt pavement that has begun to show signs of aging. Slurry seal is an excellent commercial-grade treatment alternative for asphalt with minor cracking. It fills in and conceals the cracks and is commonly used on city streets, parking lots, and industrial parks.

Slurry seal coatings are applied with a specialized slurry truck that mixes all of the components before spreading them over the road or parking lot surface. To keep costs low, slurry seal is typically recycled from old roads or parking lots and mixed with clean water before reapplying.

Slurry-sealed asphalt surfaces have a rich black color and a durable, slip-resistant surface that protects the underlying asphalt. Slurry seal also fills cracks and restores lost flexibility.

When you use a slurry seal on your parking lot, you can get a better aesthetic, a safer driving surface, and a longer lifespan out of your asphalt. Slurry surfaces are also simple to maintain and less prone to cracking due to freeze-thaw cycles. And on top of that, they won’t present many issues with gas and oil penetration as a result of leaks, so your business’s exterior will look aesthetically pleasing.

Slurry seals are classified into three types based on the size of the aggregate they contain:

Type I: Fine aggregates with diameters less than 2.36mm, commonly used in low-traffic areas such as parking lots.
Type II: Aggregate particles with maximum diameters of 6.4mm, often used to repair raveling and other more advanced states of wear commonly found on busy roadways.
Type III: Coarse aggregate chunks, commonly used to compensate for more severe surface imperfections, can also fill surface depressions, reducing the amount of water ponding.

Contractors typically avoid using Type II slurry seals on parking lots because the larger aggregate pieces can cause tire scuffing as cars enter and exit spaces.

Which Is Better: Seal Coat or Slurry Seal?

While slurry seal and seal coat are very similar, causing some paving contractors to interchange the two terms, there is one compositional difference between the two types of protective coatings.
Unlike seal coat, slurry seal has one additional ingredient: aggregate.

As the binder in asphalt deteriorates, chunks of aggregate are frequently stripped from the surface. Such areas of loss cannot be compensated for by a seal coat, which can often cause small depressions to remain on the asphalt surface, providing a place for water to pool and cause havoc.

The aggregate found in slurry seal helps to fill in those small cracks and gaps and promote a more even asphalt surface while improving overall adhesion and integration with the existing pavement. As a result, slurry seals typically outlast seal coating. Whereas contractors recommend applying seal coat to asphalt every two years, slurry seals only need to be applied every five to seven years.

Because of these reasons, South Central Sealing & Paving recommends slurry sealing over seal coating.

Choose South Central Sealing & Paving for High-Quality Asphalt Maintenance Services

When your asphalt surface needs restoration, it’s crucial that your contractor takes into account the type of asphalt being treated, its overall condition, and the general traffic flow and type of traffic your asphalt receives.

Regardless of the solution you choose, either option will need to be reapplied multiple times in the future. Still, maintenance is easier and less demanding when done correctly the first time by a team of professionals.

South Central Sealing & Paving is proud to be Wichita’s #1 asphalt parking lot sealing and repair company. With more than 30 years of expertise, our team of asphalt maintenance experts understands what it takes to deliver high-quality solutions on time, within budget, and with minimal disruption to your business.

We proudly specialize in a wide variety of asphalt maintenance services, such as crack and joint sealing, slurry sealing, pothole repair, and more, and abide by strict manufacturer specifications to ensure a final product that lasts longer.

Contact the asphalt maintenance experts at South Central Sealing & Paving today to learn more about which type of seal is best for your asphalt and how our asphalt paving and parking lot maintenance services can assist you.

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