As a property manager, keeping the parking lot in good condition is crucial for numerous reasons, from accessibility to curb appeal. You likely already know that sealing the asphalt can extend its lifespan and protect it from degradation. However, with the variety of products on the market, deciding what is best for your parking lot isn’t always obvious. Broadly, your options fall under either seal coats or slurry seals, and learning more about each can help you make this decision.
Why Asphalt Needs Sealing
Asphalt is composed of a petroleum-derived binder — which is sometimes also called asphalt — and a mineral aggregate similar to gravel. The binder is semi-fluid when hot, allowing the asphalt to be poured and spread, and solidifies as it cools to form a matrix holding the aggregate in place.
However, asphalt loses its integrity over time due to exposure to the environment. The binder becomes hard and brittle due to chemical reactions induced by oxidation and UV rays. As it ages, asphalt binder shrinks and loses its resilience against stress and water damage, making it susceptible to cracks from heavy loads and traffic. Aggregate particles also wear away from the surface, in a process called raveling.
How Seal Coating and Slurry Sealing Work
Seal coats and slurry seals serve similar purposes in pavement maintenance by protecting asphalt from the elements. However, there are key differences in how they’re used.
A seal coat is an emulsion of liquid asphalt, fine mineral fillers and anti-oxidation additives, bought and applied in a pre-mixed state. This emulsion can be sprayed onto the pavement or applied using a squeegee. The seal coat cures in about two to four hours to form a smooth protective layer over the asphalt’s surface that keeps moisture and UV radiation away from the binder.
Slurry seals are thicker because, instead of the smaller filler particles in seal coats, they contain coarse mineral aggregate much like asphalt. As a result, the slurry seal is cold-mixed on-site before application. The mixing process requires a specialized machine, which also works to apply the final product to the pavement. The slurry seal takes eight to 10 hours to cure, and the end result is similar to the underlying asphalt, producing an additional wear surface for the parking lot.
When To Seal Coat and When To Slurry Seal
Which is the best product to use for your pavement? The short answer is that there is no single best product. Slurry seals are highly resilient and better suited to filling worn and unraveled areas, because of the aggregate mixed in, and they last longer — up to 10 years, versus five for seal coats. However, the heavy equipment needed to apply a slurry seal makes it almost twice as expensive as a seal coat on average. Slurry seals should be saved for high-traffic areas, while seal coats do the job well for low-traffic areas like parking lots.
Either product will need re-applying more than once over time, though maintenance is easier and less demanding when done right the first time. As a property manager, you can best accomplish this by hiring a reputable contractor. To learn more about regular maintenance, please read our blog on The Ultimate Guide to Pavement Maintenance.
Be sure to see our infographic below to determine which is the right solution for your project. DRYCO has the tools and expertise to help you establish a maintenance plan to keep your parking lot in top condition. Contact us today to get an estimate for your project.