Date:  Thursday, August 13, 2009

Contact: Seema Javeri, WSDOT Project Engineer, (425) 401-4126 (Bellevue)
Steve Peer, WSDOT Communications, (425) 301-2023 (Bellevue)

BELLEVUE – WSDOT’s study into the use of “quieter” pavement on Western Washington highways continues this weekend on northbound I-405 through Bellevue. Crews will funnel traffic down to one northbound lane to place quieter asphalt pavement test sections.

The latest segment of quieter asphalt pavement is the third test section in the region for this study. The previous two test sections were installed on southbound I-5 through Lynnwood in 2006 and on SR 520 between Medina and Bellevue in 2007. The data collected by WSDOT engineers shows the first two test sections are not performing well. But experts believe this third section is different from the previous tests and may perform differently.

“So far, our quieter pavement test sections are not performing well,” said Tom Baker, WSDOT State Materials Engineer. “Any audible noise reduction was lost within the first six months after paving. Today both quieter pavement test sections are just as loud to the human ear as sections paved at the same time with our standard asphalt.”

But, the experiment is not complete just yet. WSDOT pavement engineers still see a value in testing quieter asphalt pavement on I-405 in Bellevue using different methods and different additives than used in other places.

• Temperature: WSDOT crews will install the quieter asphalt pavement test section this weekend when temperatures are expected to be above 70 degrees. Quieter pavements have proven successful in states with warm climates such as Arizona, California, Texas, Georgia, Alabama and Florida. Engineers believe that the temperature during paving may affect the long-term durability and noise reduction capabilities.
• Paving over concrete: This test section will be installed over existing concrete. WSDOT engineers want to know if installing quieter asphalt pavement over a rigid concrete base improves the pavement’s durability and noise reduction capability. Previous sections were applied over asphalt.
• Pavement mix: Crews are altering the quieter asphalt pavement mixtures on this test section. The formula is closer to the mix used by the Arizona Department of Transportation. It calls for the addition of lime and a different grade of oil applied to the roadway surface prior to the placement of the quieter asphalt pavement. WSDOT engineers want to know if these factors will affect the durability and noise reduction capabilities of the quieter asphalt pavement.

The paving is part of a $124 million construction contract that adds lanes to both directions of I-405 in south Bellevue. Construction is scheduled to be completed this year and includes one new northbound lane between 112th Avenue SE and SE Eighth Street and two new southbound lanes from SE Eighth Street to I-90. The project is funded by the 2003 and 2005 gas tax packages.

Next steps

WSDOT will monitor this section of quieter asphalt pavement for five years or until they've determined the pavement has reached the end of its useful lifecycle. This information will help WSDOT make more informed decisions about incorporating quieter asphalt pavement into highway projects.

For information on quieter pavement please visit: www.wsdot.wa.gov/Projects/QuieterPavement/

For information about I-405 construction projects please visit: www.wsdot.wa.gov/Projects/i405/112thAvetoSE8th/

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