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Civil engineering researcher’s test device adopted by national transportation organization

Rylie Miller | Oct 28, 2019
ABCD Dr. Kim

Civil engineering researcher’s test device adopted by national transportation organization

Rylie Miller | Oct 28, 2019

An Ohio University professor’s method of checking the durability of asphalt in low temperatures has been adopted by the American Association of State Highway and Transportation Officials (AASHTO) as a regular specification.

Since 2003, Russ College Associate Professor of Civil Engineering Sang-Soo Kim has been studying the point at which asphalt pavement cracks in low temperatures. Not only were existing test methods too difficult to perform, but they resulted in incomplete findings and data – so Kim developed the Asphalt Binder Cracking Device (ABCD).

Previous test methods only measured the material’s flexibility, or stiffness, and involved a tedious process. However, the ABCD – a disc-shaped, silicone mold with an inner ring where heated liquid asphalt binder is poured – tests for the low temperature performance, which is affected by the material’s stiffness, strength and the speed at which it shrinks in low temperatures. The ring containing the asphalt binder sample is then connected to a data recording system via wires and placed in an environmental chamber. The test begins by cooling the chamber by 20 °C per hour to about -60°C (-76° F).

“As temperature decreases, asphalt binder shrinks and the inside ABCD ring restricts the sample from shrinkage, generating thermal stress,” Kim explained. “The stress in the asphalt sample is measured by the strain sensor located inside of the ABCD ring, together with the current sample temperature.”

Assistant Professor of Civil Engineering Issam Khoury provided support for instrumentation of the sensors, and programming, to enable Kim to first develop a primitive version of computer software that records data from the ABCD’s sensors. Thanks to a grant later on, Kim worked with additional developers to improve the software and test device.

The ABCD simplifies previous testing methods to ensure ease of use and interpreting of test results. The environmental chamber is programmed to shut off once the sensors detect the binder has cracked, so the device needs less supervision.

“At the DOT (Department of Transportation) lab all the testing is done by technicians – the engineer isn’t always there,” said Kim. “So the simpler the test, the easier to implement. I think anyone can perform this test.”

The ABCD’s materials also make cleanup much easier than traditional asphalt binder tests.

“Asphalt doesn’t come off easily,” said Kim. “But because the test mold is made of silicone, you can just wipe it -- you don’t need to use a solvent.”

The device can be used in industries such as asphalt production, federal/state highway agencies, contractors, and in teaching and research institutions.  

Currently being used for various studies on improved paving materials, the ABCD has the power to influence Ohio’s highway construction and repair activities. Due to the state’s cold winter climate, premature low temperature cracking of asphalt pavements is very common and leads to expensive repair or reconstruction.

Four ABCD units have been sold to Russia, where the test has also been adopted.

Marissa McDaid and Colleen Carow contributed to this story.