Applications & Innovations - Mixing Quiet
Applications & Innovations
by Lauren Heartsill Dowdle
Where the Rubber
Quiets the Road
Creating mixtures for smoothness and low noise
G
rinding, loud, uneven roads can leave drivers and
their vehicles shaken up after a long ride. So it’s no
surprise that road conditions are the public’s No. 1
criterion for satisfaction, according to a 2002 Federal Highway Administration (FHWA) survey.
“Noise can affect the passengers in a vehicle, as well as the
people living and working along a road,” says Trenton Clark,
director of engineering, Virginia Asphalt Association (VAA),
in Richmond, Va. “The owner should keep that in mind
when specifying a treatment for a roadway – either new
construction or resurfacing. It is a balance between managing
costs and benefits.”
And although a road project’s checklist might not include
the end-user’s approval, smoothness standards and specifications continue to be an important part of many road builders’ contracts and planning stages.
“Several factors go into achieving a smooth ride: mix design, mix delivery to the project, proper paver operation and
compaction,” Clark says.
But eliminating bumps is not the only, or main, benefit
of laying an even surface – a National Cooperative Highway
Research Program analysis shows improved smoothness
extends pavement performance life by up to 50 percent.
“Transportation agencies have a goal to provide the lowest lifecycle cost for road treatment,” says Jim Barnat, vice
president of innovation, Road Science, a division of ArrMaz.
“As secondary considerations, these agencies look at aesthetics, ride quality and quietness characteristics. They generally
focus on durable pavement structures and crack-resistant surfaces, providing the best return on their investment.”
On the road to create lasting, smooth surfaces, some have
stopped to address noise concerns, as well. These departments of transportation, including those in Arizona, Florida,
Minnesota and Kansas, have tested pavement alternatives
by using rubberized-asphalt mixtures near residential and
sound-sensitive areas to decrease the traffic noise.
“Road noise is generated from two main sources – a vehicle’s engine/drive train and the tire-pavement interaction,”
Clark says.
Virginia roadbuilders conducted an experiment with various surface mixes and aggregate sizes with the goal of discovering which materials created quieter, yet smooth, roads.
The Experiment
When a bill was introduced in Virgina in 2011 to develop
quiet-pavement technologies to aid in sound mitigation, the
Virginia Department of Transportation (VDOT) constructed
road demonstrations to test various surface mixtures.
VDOT and its asphalt industry partner, the VAA, created
noise-reducing surface mixes to be used on the projects,
Better Roads December 2012 33