Connections

Issue 2 • Volume 3 • April 10

ENVIRONMENT

Asphalt Goes Green in Rapid City
By Roger Hall, P.E.

Hills Materials Company in Rapid City, S.D., is the first to place foamed warm-mix asphalt (WMA) in the state. WMA was used on a project in a residential neighborhood through a cooperative effort that included the city of Rapid City, the South Dakota School of Mines and Technology, the South Dakota Department of Transportation and Hills Materials Company.

Hills Materials sponsored a seminar, including a plant tour and project visit featuring Ron Sines, P.E., Oldcastle Materials; Lance Roberts, PhD, P.E., South Dakota School of Mines; and Ken Sweeden, Dakota Asphalt Paving Association. More than 50 people attended the seminar, including consulting engineers, city, state and county engineers, city councilmen, a department of transportation commissioner and county highway superintendents.

Ron Sines provided an overview of WMA, covering global and national perspectives and a brief history. He demonstrated how asphalt can be recycled repeatedly and retain its mix quality and integrity.

Ken Sweeden covered the status of asphalt technologies in the Dakotas. Ken is an advocate of recycling asphalt products and works with governmental agencies to change specifications for public works projects. He also addressed the use of open-graded friction course and porous asphalt and their proper applications.

Lance Roberts discussed current research projects involving WMA technologies, the use of fibers in asphalt and the more technical aspects, such as resilient and dynamic modulus testing.

Following the seminar and TAKE-5 by the Hills Materials safety director, attendees visited the plant and street project, where the plant manager demonstrated the latest asphalt production technology. Participants observed WMA performing as well or better than hot-mix in the lay down process.

Asphalt Goes Green The Rapid City project involved the placement of several types of mix and is being used by the DOT and the city as a test project. The mixes used on the project include: WMA with 15 percent reclaimed asphalt pavement (RAP), hot-mix with 15 percent RAP, WMA with fiber reinforcement, hot-mix with fiber reinforcement, and WMA with 10 percent RAP and 5 percent recycled shingles. Each mix was placed adjacent to a differing mix to monitor the performance over time.

Generally, the asphalt lay down crews preferred WMA and pointed out that it's easier to work with and compaction is simpler. Testing has shown the WMA has more consistent air voids and compaction, and there is no difference in the appearance of warm-mix when compared to hot-mix.

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