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The most common road surfaces today are Hot Mix Asphalt (HMA) pavement and Portland Cement Concrete (PCC) pavement. Both types of pavement can be modified to create quieter pavement surfaces.
Hot Mixed Asphalt (HMA) is also commonly used on Washington State's urban highways. Most HMA pavement is "dense-graded" - it has a tight surface with few air pockets, which minimizes the ability of water to enter its surface. As a result, dense-graded HMA pavements have good durability and skid resistance, but also tend to be slightly louder than Open Graded Friction Course (OGFC) pavement.Open Graded Friction Course (OGFC) asphalt pavement is quieter than dense-graded HMA because it has "negative texture" - air pockets in the pavement that capture road noise. In addition to reducing noise, OGFC pavements have excellent skid resistance, and also reduce splash and spray from tires by draining water through the pavement rather than across the pavement surface. The down side of OGFC pavements is that they have deteriorated more quickly in the past than dense-graded HMA pavements. We tested earlier generations of OGFC on I-5 in western Washington in the 1990s. These projects deteriorated rapidly and developed ruts (as shown above). The average lifespan was just four to eight years before the roadway had to be replaced. Many technological advances have been made since quieter asphalt was last tested in Washington State in the 1990s. We are testing two new mixes - asphalt modified with rubber and asphalt modified with polymer - to see if they perform better.In September 2006, crews installed the first test section of quieter asphalt on southbound I-5 in Lynnwood.
Portland Cement Concrete (PCC) is often used on heavily-traveled urban corridors because of its durability. Most PCC surfaces (like the one shown above) are "tined" to provide skid resistance for drivers. Tining is created by dragging a mechanical rake across freshly laid concrete to create shallow channels. Tined PCC is one of the most durable but also one of the noisiest pavement types.We can make PCC quieter by using different texturing techniques, including longitudinal tining, grinding and carpet drag methods, to change the pavement surface and thereby reduce noise. The photo above shows concrete being longitudinally tined on I-5 south of Tukwila.The photo above shows crews using Astroturf™ for the carpet dragging technique on a test section of quieter concrete on I-90 in Spokane.Crews install concrete on I-90 in Spokane.