Basic Asphalt in a Nutshell: Bottom of the Barrel

  Asphalt is literally whatever is left over in the bottom of the barrel after crude oil is refined. Refining oil breaks it down into kerosene, gasoline, naphtha and other lighter fractions. Literally asphalt is the goo that is made up of about 80 percent high molecular weight hydrocarbons. Aside from its dark brown or black color, its most noteworthy characteristics are that it is sticky, flexible and water insoluble.

  Asphalt is so sticky, it has trapped dinosaurs who couldn’t break free, and it’s so waterproof, it has been used to caulk wooden ships and line drinking water reservoirs.

  Dating back to Roman times, all paved roadways have been made of rock – gravel to prevent people and vehicles from sinking in the mud. But gravel alone quickly gets pushed down and scattered by traffic. And, with the invention of the automobile, gravel roads created magnificent dust clouds for motorists and forced them to wear those loopy driving goggles.

  The solution? Spray tar on top of the gravel to hold it together, eliminate dust and prolong the life of the gravel road. In addition, the flexibility of asphalt helps it adjust and conform somewhat to the weight of traffic.

  Often, in summer months, asphalt may get a little too flexible to the extent that traffic leaves ruts behind. Similarly, in cold weather, asphalt can become so brittle, it cracks under traffic.

  Finding the best recipe for the perfect paved roadway is the point of the asphalt business today. There are hundreds of paving techniques, methods and modifiers to help asphalt last longer and provide a smoother, more durable result.