An engineer’s invention could reduce the cracks, bumps, and potholes plaguing the nation’s highways
October 28, 2011
Sang-Soo Kim used to contemplate this problem during his weekly commute between his job in Athens and Columbus, Ohio, where his wife was a graduate student at Ohio State University. “At first, I listened to music and listened to radio,” he recalls. “It’s a two-hour drive, and it’s enough time to think about my research.”
A civil engineer, Kim’s expertise is the petroleum binders that hold road asphalt pavement together. A major frustration for Kim and others in the transportation industry was their inability to accurately predict the temperature at which a particular asphalt binder would crack. A more precise testing system could help officials invest in asphalt blends that would be more durable for certain climates.
Sang-Soo Kim. Photo Courtesy of the Innovation Center.
It’s an issue with hefty financial implications. The Ohio Department of Transportation (ODOT) spends up to $1.5 billion on road construction and $15 million to $20 million on asphalt-related maintenance annually. The federal highway budget comes in at $40 billion a year. On the consumer end, an U.S. Environmental Protection Agency analysis shows that poor road conditions, on average, contribute to a 4.3 percent reduction in fuel economy, with a maximum fuel economy reduction of 50 percent.
As Kim traveled back and forth on U.S. Rt. 33, he had a brainstorm. “One day I sat down in my office and started drawing some diagrams,” recalls Kim, an associate professor of civil engineering at Ohio University. “I had a rough draft and did some theoretical calculations.”
With that, the Asphalt Binder Cracking Device, or ABCD, was born. Patented in 2007, the ABCD easily incorporates a binder’s stiffness, strength, and thermal expansion coefficient (which is how its volume changes with temperature) into the testing process. The invention features a small, ring-shaped test bed that Kim can place in an environmentally controlled chamber—which looks like a small industrial refrigerator—to record the exact temperature point at which the binder will crack.
“ABCD determines the low-temperature performance of asphalt binders in field-like conditions,” Kim explains. “Asphalt will stretch out, but once the temperature continues to drop, asphalt becomes brittle and cannot take the stress.”
He holds up a 2-inch diameter ABCD ring, which resembles an oversized wedding band, silver in appearance but made of an alloy that experiences virtually no contraction under temperatures in a chamber that can drop to minus 60 degrees Celsius (minus 76 F). The ring sits in a slightly larger-diameter silicone mold.
Asphalt binder is poured into the space between. On the inside of the ring are electronic sensors that measure temperature and strain. The latter records the asphalt binder compression when the material contracts under cold temperatures, as well as the sudden release of pressure when it breaks. These sensors are connected to a computer that gives results in Microsoft Excel.
“What speaks highly to Dr. Kim’s abilities and approach is that he took basic engineering theory and engineering materials knowledge and applied it very intelligently,” says Dave Powers, a materials engineer with ODOT. “He took something very simple and made it work. Other people tried this in the past and were not entirely successful.”
After Kim finally made his breakthrough, it was time to manufacture a prototype. He first worked with the machine shop in the Russ College of Engineering and Technology, and later with professional fabricators, to create a workable ABCD.
In 2008, Kim licensed the technology from Ohio University and created a start-up firm, located in the university’s Innovation Center, to commercialize and market the invention.
“When I started the company and had to make a name for it, I just came up with EZ Asphalt Technology,” Kim says. “That’s basically what it’s all about. I wanted to incorporate the technology, and I wanted people to use it easily.”
Kim’s road to commercializing the ABCD has been relatively smooth. He has received roughly half a million dollars in research grant funding, including $225,000 in 2008 from the Federal Highway Administration’s Highways for Life technology partnership program. This grant also provided money for a handful of Federal Highway Administration offices to purchase the ABCD. Kim also has received funding from the state of Ohio’s Enterprise Appalachia program, as well as from the federal Transportation Research Board and ODOT.
In 2011, the ABCD test method was adopted as a national standard in the American Association of State Transportation and Highway Officials (AASHTO) specifications. Kim’s next goal is for the Federal Highway Administration to recommend that AASHTO adopt ABCD as a grading test method, meaning that all asphalt produced and sold in the United States would need to be tested with the device.
If so, EZ Asphalt Technology would likely see a boost in business. Each batch of asphalt binders needs to be tested for durability, due to subtle differences based on the petroleum source, the refinery, and the additives. The ABCD could have financial implications for the taxpayer as well, considering the overall costs of road construction and maintenance.
ODOT’s Dave Powers says his team has set aside money in the department’s proposed 2012 budget to purchase Kim’s device. With a current price tag of about $50,000, Powers considers the ABCD a good investment. “I think you look at that in light of how many million tons of asphalt go down in the state every year, and the most expensive component of the asphalt is the asphalt binder,” he says. “Anything we can do to ensure or enhance performance of those binders is a plus.”
Although Kim is no longer commuting between Athens and Columbus, he’s still thinking up new ways to reduce the need for those orange barrels along U.S. roadways. Up next? A similar device to test concrete. He holds up a sample, which looks like its asphalt predecessor except that it’s the size of a barbell weight. And Kim would like to commercialize a third measurement device for the study of flow of soft solids such as asphalt and concrete. The name? Kim is keeping it simple: the Easy Flowmeter using Gravity, or EFG. The rest of the alphabet awaits this civil engineer’s imagination.
By Mary Reed
This article will appear in the Autumn/Winter 2011 issue of Perspectives magazine, which covers the research, scholarship, and creative activity of Ohio University faculty, staff, and students.