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Where the rubber meets the road: Wisconsin asphalt research yields energy savings

Emil Bautista

Civil and environmental engineering graduate student Emil Bautista prepares asphalt samples for testing in the Superpave Gyratory Compactor to determine their volumetric and mechanical properties. (large image)

In an effort to conserve energy and reduce the environmental effects of building asphalt roads, a team of University of Wisconsin-Madison civil engineers is studying ways to modify asphalt and develop new, more sustainable processes for producing the material.

“Significant amounts of energy are required to heat asphalt mixes for pavement construction,” says Hussain Bahia, a UW-Madison professor of civil and environmental engineering. “If we can modify hot-mix asphalt (HMA) mixes so that pavements can be laid at lower temperatures, the energy savings at the time of construction can be significant. Moreover, if we can extend the longevity of these mixtures, it will save even more energy required for rebuilding pavements.”

The task is not a simple one. Modified asphalt pavements must perform as well as or better than today’s pavements. In addition, the researchers must carefully assess existing tests and update specifications to accommodate the novel asphalt mixes.

The rewards, though, are worth the investment. “Beyond energy savings, resources can be even further conserved by increasing the use of recycled paving materials,” says Bahia. “At the same time, we are aiming to modify asphalts to be more resistant to failure due to the impacts of traffic and climate and thus reduce the need for repair, which is very energy intensive.”

Recently, UW-Madison asphalt researchers and colleagues around the country received a significant boost: A grant from the Federal Highway Administration funded the Asphalt Research Consortium (ARC), an organization that joins researchers with the breadth and depth of experience to address critical issues related to asphalt pavements. The ARC coordinates much of its work with national experts in cutting-edge asphalt technology; in addition to UW-Madison, ARC members include Western Research Institute, Texas A&M University, University of Nevada-Reno, and Advanced Asphalt Technologies LLC.

To reduce the risk of pavement failures, ARC researchers hope to improve how asphalt mixes resist moisture damage, fatigue and thermal cracking by increasing their understanding of these damage mechanisms. In addition, they will introduce and implement next-generation engineered pavement materials.

UW-Madison pressure distribution analyzer

The patented UW-Madison pressure distribution analyzer measures forces exerted on asphalt samples in the compactor in real time. (large image)

The UW-Madison team is leading ARC efforts in modified, or “engineered,” asphalts.

Consortium members signed their five-year research contract with the Federal Highway Administration in May 2007. Already, Bahia’s team has performed critical groundwork in developing theoretical models and adapting lab and field tests to advance asphalt technology.

Beyond the scope of the Asphalt Research Consortium, Bahia sees additional pressing needs for investigating modified asphalts in cooperation with both petroleum producers and additive manufacturers. To this end, he is formally proposing a university center dedicated to modified asphalt research: the UW-Madison Modified Asphalt Research Center (MARC). “We envision MARC as a cross-departmental center to define, address and advance all aspects of modified asphalts,” he says.

UW-Madison asphalt research team

A diverse and experienced team from UW-Madison is conducting research with the Asphalt Research Consortium. The UW-Madison team includes two faculty members, four research staff members, six graduate students and four undergraduates. Two additional faculty members at other UW System campuses also are involved in the effort. (large image)

The UW-Madison interdisciplinary asphalt research team includes experts in civil and environmental engineering, geological engineering and chemistry, including Civil and Environmental Engineering Professor Bahia, Associate Researcher Codrin Daranga, Researcher Haifang Wen, Assistant Professor Dante Fratta, research intern Carl M. Johnson and Administrative Program Specialist Andrew Hanz.