Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/85913
RoadScience by Tom Kuennen Contributing Editor SPECIAL SERIES A Liquid asphalt binder might be thought of as the sludge left over from petroleum after higher-revenue products such as gasoline, plastic feed stocks, kerosene and petroleum distillates have been removed. About 3 percent of a barrel of petroleum (42 gallons) winds up as liquid asphalt. "Asphalt literally is the bottom of the barrel," says The Chemistry of Road Building Materials Asphalt a la Carte P 16 April 2012 Better Roads Modifi ers Control Mix Performance etroleum (literally, rock oil) is one of the most important gifts of the union of carbon and hydrogen. But instead of being a simple compound (like water), petroleum is a natural prod- uct, a complex "soup" of thousands of hydrocarbon compounds, the mix varying according to source. The never-ending variance of the makeup of petroleum challenges the refi ner, who must adjust the refi ning process to optimize extraction of the valuable compo- nents of petroleum. Codrin Daranga, Ph.D., technical manager, Blacklidge Emulsions. "It is the waste left over at the bottom of the distillery after more valuable hydrocarbons have been extracted. At one time refi neries would give away the liquid asphalt for the price of transportation, just so they would not have to deal with it. Now there is such a need – with so little liquid asphalt available – that we pay top dollar for it." As the demand for gasoline and plastics have in- creased, refi neries have gotten better at removing those "light" products from the source crude. As those value- added products are removed, the "richness" of what's left over as liquid asphalt is diminished. "The industry has gotten better at refi ning petro- leum," Daranga says. "It stands to reason that more valuable product has been extracted than ever before, and there is less in the remaining liquid asphalt. But it depends on the refi nery. Some refi neries are geared almost entirely to making gasoline; that's what they're designed to do. There will be very little asphalt from those plants, and it won't be very good. For them asphalt is a waste and they will do everything they can to minimize that waste. "But there is another kind of refi nery that is geared only toward making asphalt," Daranga says. "Its busi- ness model is to make asphalt, so that end product will be quite good." Such a dedicated refi nery in Louisiana is scheduled to come online this year. "Without a doubt, over the last 20 to 30 years, refi ners have gotten better at extracting all the high- value materials they can out of the source crude," says Bob Kluttz, senior scientist, research and development, Kraton Polymers. "This includes a variety of technolo- gies, different distillation and extraction techniques as well as coking. You can take asphalt that once was $100 to $200 a ton, and turn it into light ends and gasoline which sell for much more."