Asphalt FAQ Page

How is asphalt made, and what is asphalt made of?

Asphalt is typically made of gravel, sand and crushed stone (called “aggregates”) with a petroleum-based binding agent. The binding agent is what gives fresh asphalt its black color and tar-like odor.

Who invented asphalt?

Asphalt is a natural material that humans have used since ancient times! Builders in ancient Babylon used asphalt to waterproof temples and build brick walls.

Asphalt was first used for streets and walkways in the United States in 1870. Edmund J. DeSmedt, a Belgian chemist, was the first to build a genuine asphalt road in front of the city hall building in Newark, New Jersey. In 1871, Nathan B. Abbott of Brooklyn, New York, filed the first asphalt patent.

Can you put asphalt over concrete?

Concrete is an excellent foundation for asphalt. Many state highways, county roads, interstates and local streets have an asphalt overlay over a concrete base. But while asphalt over concrete is the standard for road construction, not all concrete surfaces can withstand a successful asphalt overlay.

Sometimes, the ground beneath a concrete surface shifts over time. This can cause sections of the concrete to shift, too, or be forced upward. You’ve probably seen this on driveways or sidewalks. The more uneven the concrete, the less likely the chance of a successful asphalt overlay.

Additionally, concrete surfaces are poured in stages, with fissures (expansion joints) between them. These expansion joints can widen as the ground freezes and thaws. Wide gaps between concrete slabs can cause large cracks in an asphalt overlay that are difficult to fix.

How long does asphalt take to dry?

Asphalt typically dries in 48–72 hours. Extreme heat and humidity can delay the drying process, so it’s best to avoid scheduling asphalt repairs when temperatures exceed 100 degrees Fahrenheit.

There is a difference between asphalt dry time and asphalt cure time. While asphalt may be dry enough to drive on within a few days, it takes up to a year to fully harden (cure), and about a month before it’s cured enough to seal. Fully cured asphalt is gray in color instead of the black of new asphalt.

How long before you can drive on new asphalt?

You can typically drive on new asphalt after 48–72 hours. At that point the asphalt is typically dry enough to withstand normal traffic. However, asphalt that hasn’t yet cured (hardened) may be damaged by heavy-duty loads and equipment. It’s best to discuss this timeline with your contractor.

How long does a sealcoat take to dry?

You should allow at least 24–48 hours for your sealcoat to dry. However, drying time varies depending on the weather conditions.

How to dry asphalt faster?

Four factors that play a significant role in drying asphalt:

  • Temperature
  • Humidity
  • Sunlight
  • Wind

The higher the temperature, the faster the evaporation and consequently the dry time. However, if the temperature is too high, the heat can cause the asphalt to soften and delay the drying process.

Moisture also plays a critical role. The more moisture in the air, the less absorbent it becomes, resulting in a more extended waiting period for your asphalt to dry.

Sunlight also plays a role, as heat is both created and renewed by sunlight. As a result, less sunlight results in less heat renewal, resulting in a longer dry time.

Lastly, wind also plays a role in the drying process, as it can speed up the evaporation process and reduce the amount of time the asphalt takes to dry.

Can asphalt be laid in the rain?

Asphalt is laid down as a liquid or semi-solid before it dries and solidifies to form pavement. When asphalt is laid down in the rain or on wet ground, the moisture repels the material wherever it comes into contact, creating abnormalities such as cracks and craters.

How long should sealcoating last?

Sealcoating is often recommended every three years. However, older asphalt or asphalt that is frequently used (i.e., parking lots) may need to be sealed annually.

Will asphalt sealer stick to concrete?

No. If applied to concrete, asphalt sealer will be absorbed into the porous surface and bind with the microscopic particles inside, instead of sitting on top of the surface to form a protective layer.

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