What Is Asphalt?

Asphalt paving with HMA Paving and Contracting

People often ask, “what is asphalt?” Commonly known as “blacktop,” asphalt is a material used for commercial road building and private driveway use. It is made from a combination of stone, and silica sand, with a type of liquid asphalt as the glue that holds the materials together.

These three materials as well as other fillers make up blacktop. They are heated to a high temperature and blended together. Multiple grades or “sizes” are produced to meet specific job needs. Highway asphalt has generally larger stone and multiple layers. Driveways do not require the same material depth a road needs, but in most cases have a finer top layer of asphalt for aesthetic purposes.

History of Asphalt

As early as the Roman days, road building was a part of society. Early Romans used slaves to build roads from available materials constructed in a flat surface. This enabled easier transportation throughout their sprawling empire.

In the late 1700s, John Loudon McAdam refined the art of road building. His plan was to raise roads built out of stone to the surrounding areas. This allowed for drainage of the newly constructed road. His method was to grade a certain parcel of land, install fragmented larger stone, and then place small size stone as filler. Stone dust was added to “choke” the material, locking it in place.

This has evolved to today’s use of bitumen, a distilled petroleum product blended with stone and silica sand to produce asphalt. Bitumen is distilled from select crude oils. Alberta, Canada has the largest reserve of crude oil deposits.

How Is Asphalt Classified?

Asphalt is broken down into classifications based on the size of the aggregate. Base asphalt

has stone as large as 1 ½”. This is known as type 1 base. Binder, also known as type 3 or intermediate size, has aggregate as large as ¾”. Type 6 top asphalt, commonly used for heavier road or parking lot construction, has stone up to ½”.

Type 7 asphalt has stone generally up to ¼” and is a finer asphalt product used in residential driveway construction. This type of asphalt, with its various fillers, rolls in tighter and has an aesthetic value to its appearance.

Contact HMA Paving and Contracting Today

If you are interested in learning more about asphalt, HMA Paving & Contracting is here to help! We’re happy to answer any questions you may have about what it takes to maintain your parking lot or roadway over time. Fill out our form or call (518) 664-1014 to get in touch today!