Industrial Chemistry: For Advanced Students - Mark A. Benvenuto 2015


Asphalt still has the older name “bitumen” attached to it and can also be called “tar,” depending on the circumstances in which it is used and the source materials. Recovered from the heaviest fraction of crude oil, the viscous substance used in making roadways is a mixture of heavy hydrocarbons, and when mixed with stone becomes essentially a hydrocarbon-based concrete. Asphalt is used predominantly in road construction, and to a lesser extent as a waterproofing material, often for commercial or residential buildings.

The United States Geological Survey Mineral Commodity Summaries does not track asphalt, but it does track sand and gravel as a category, as well as crushed stone (US Geological Survey, 2014). Both are plentiful and widespread, and both can be mixed with asphalt as it is being prepared for use.

25.1 Source material

In almost all cases, the source material for asphalt is the heaviest fraction of crude oil, the fraction that cannot be broken into some smaller hydrocarbon even at elevated temperature and used either as a feedstock for some plastic or as a motor fuel or motor fuel additive. Thus, asphalt production is tied to crude oil refining.

When used as a road material, asphalt is more properly called asphalt concrete, because it is mixed with stone, and can comprise more than 90% stone and other additive material. Asphalt serves to bind the other aggregates together.

25.2 Formulations and production

Formulas for asphalt are difficult to write and represent in terms of traditional Lewis structures or molecular formulas, because it is a complex mixture of heavy hydrocarbons and multiple fused polycyclic hydrocarbons. Also, since asphalt can be so viscous that it does not flow, it can be mixed with other materials — usually lighter, liquid hydrocarbons — to make the end product easier to use and apply. However, this also makes the mixture more complex. In all cases except what is called “cold patch,” asphalt is heated prior to use. When asphalt must be transported long distances and kept hot for the entire transport, trucks are sometimes used that have the hot exhaust gases from the engine evacuated through tubes which help keep asphalt in a state where it can be worked upon arrival at its destination.

25.3 Uses

Close to 90% of asphalt is used for road construction. Other materials that compete with it for this use are stone, brick, and interlocking paving brick, each of which is not made with a hydrocarbon source as a starting material.

Asphalt is used to a lesser extent for waterproofing building roofs. Generally, commercial or corporate buildings that have large, flat roofs are waterproofed in this way, but some residential housing is as well. Asphalt shingles are used on houses in large parts of the world, but compete with several other different types of roofing material, such as ceramic tiles.

The difference in asphalt when used in road construction versus roofing water proofing is often a difference in what additives are mixed with the starting material. As mentioned, asphalt is often so thick that it does not flow, and thus some lighter hydrocarbon is mixed with it to lower its viscosity. Kerosene has been used in the past, but it is being displaced by other liquids that are considered environmentally more benign. This is driven by the fact that when road material is put in place, the kerosene simply evaporates into the surrounding atmosphere.

A smaller use for asphalt than these two is inks and paints. Paints and inks made with asphalt tend to have high resistance to weathering, and are thus used in outdoor applications.

25.4 Reuse and recycling

When it comes to recycling of commodities, most individuals think in terms of paper, plastic, glass, or aluminum. These are definitely the products recycled from residences the most. But asphalt is routinely recycled when a road or parking area is resurfaced. Indeed, the National Asphalt Pavement Association refers to asphalt as, “the #1 recycled product in America” (National Asphalt Pavement Association, 2014). Both the Association of Modified Asphalt Pavers and the Asphalt Institute also point out the re-cyclability of asphalt (Association of Modified Asphalt Producers, 2014; The Asphalt Institute, 2014). In general, the only time asphalt is disposed of in a landfill is when the area being dug up could no longer be used as a road or a paved surface. Even in such cases, if other construction projects requiring asphalt are underway nearby, it can simply be trucked to the new site and used there.


A relatively new term in the lexicon, “bio-asphalt,” means asphalt produced from some renewable, nonpetroleum-based source. The advantages in using bio-asphalt are rather obvious, that no petroleum is consumed in its production, and that carbon-based material which might otherwise be unused, and disposed of in landfills, is utilized in making it. True bio-asphalt can be made from a wide variety of natural sources, such as corn, molasses, potato starch, or sugarcane residues. Some firms have already begun marketing bio-asphalt, but have chosen to keep their formulas proprietary. Usually such firms promote the material in terms of its environmental friendliness. For example, Avello Bioenergy states at its website: “Bioasphalt binder is produced from domestic nonfood resources such as agricultural and wood residues. Using biomass derived Bioasphalt binder decreases our national demand for imported petroleum” (Avello Bioenergy, 2014).

Also, a material can be called bio-asphalt when it is made from once-used engine oils, although this is more properly asphalt that has been made from a petroleum base, but used once prior to its conversion to asphalt.


The Asphalt Institute. Website. (Accessed 30 January 2014, as

Association of Modified Asphalt Producers. Website. (Accessed 30 January 2014, as:

Avello Bioenergy. Website. (Accessed 1 June 2014, as:

National Asphalt Pavement Association. Website. (Accessed 30 January 2014, as:

US Geological Survey, Mineral Commodity Summaries 2013. Website. (Accessed 26 January 2014, as: