How Asphalt is Made

Asphalt Production Rises as Winter Ends and Road Construction Season Nears

photo of asphalt road under construction

In the northern part of the U.S. where ProQuip is located, there are two seasons: winter and road construction season.

With winter finally over (hopefully – it snowed last week, but 80 degree highs are in the 10 day forecast), orange barrels will soon line many of our pock-marked roads to manage traffic during ubiquitous summer re-pavement projects. The majority of projects will use asphalt.

Most of us are very familiar with the use of asphalt as a road surface and other common ground surface applications including parking lots, trails, tennis/basketball courts and airport runways. Asphalt is also used in various construction products including roofing materials, rust inhibitors, sealants, waterproofing, soundproofing and road oils (sprayed to settle dust and bind gravel).

Many are likely not familiar with asphalt’s origin, chemical composition or manufacturing process. This In The Mix blog takes a closer look at the history of asphalt and how asphalt is made.

What is Asphalt?

Asphalt is one of several mixtures of hydrocarbons called bitumens (or pitch). It is obtained from natural deposits/brea (e.g., La Brea Tar Pits) or as a petroleum industry byproduct. Alberta, Canada has most of the world’s natural asphalt reserves in the Athabasca oil sands, an area larger than England.

Natural and refined asphalt have the same durability. The latter has more uniformity and few if any impurities.

The History of Asphalt

Early uses of asphalt included mummy preservation. Photo by Robert Thiemann on Unsplash

Asphalt is one of the world’s oldest engineered materials. In 6000 B.C., Sumerians used natural asphalt to waterproof ship hulls. Later, other ancient civilizations used asphalt as a mummy preservative and building/paving block mortar.

The uses for natural asphalts continued to expand until the early 1900s when refined asphalt was discovered and automobile use surged. The popularity of cars increased the demand for new roads and need for asphalt supply.

Asphalt technology continues to advance including production of synthetic asphalt from non-petroleum alternatives (one alternative uses sewage sludge). Additionally, “smart” asphalt could use modifiers to change its physical characteristics when moisture is present to improve tire traction.

How Asphalt is Made

Refined asphalt is made from the distillation of crude oil. Asphalt is the heavy residue of this process. Several “lighter” products made from crude oil distillation include paraffin, gasoline, naphtha, lubricating oil, kerosene, and diesel oil.

Following the distillation process, asphalt may be blended with other products to alter its curing rate (slow, medium, rapid), modified with polymers or other materials to improve performance (e.g., better crack sealing) or emulsified with water and other agents to facilitate pumping and spraying.

Most asphalt used in paving projects is either hot-mix (heavy use) or cold-mix (light/medium use and patching; typically blended or emulsified).

Hot-mix asphalts made using a batch process mix aggregate (e.g., gravel) with asphalt cement in a pugmill. Heat is applied to each component before mixing to remove moisture from the aggregate and to make the asphalt more fluid. Drum-mixing processes heat and blend the aggregate with asphalt at the same time in a drum mixer.

Hot and cold-mix asphalt can be used immediately or held in storage tanks. Stored asphalt requires controlled environmental conditions and continuous agitation.

For More Information

ProQuip tank agitators are used for modified asphalt production and large asphalt storage tanks throughout North America. For more information on ProQuip mixing solutions for asphalt manufacturing, email or call us at 330-468-1850.

Sources: Wikipedia, How Products are Made