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One major advantage to using
an asphalt rubber binder in a pavement is the increased pavement
life through better resistance to cracking and fatigue caused
by heavy traffic. Case studies have  proven
again and again that asphalt rubber materials, when designed
properly will last much longer than conventional un-modified
asphalt materials.
Asphalt-Rubber pavement materials
have undergone some of the most extensive pavement testing protocols
known to man and have always come out as the best. For agencies
that have used asphalt-rubber, better long-term field performance
is expected.
Take a look at test sections placed
on I-40 near Flagstaff, AZ. These photographs taken after 8 years
of tough field performance in a climate at 7000 feet in elevation,
100 inches of snow each year and temperature ranging from 20
degrees below zero to 100 degrees F. The pavement on the left
is a 4 inch thick conventional overlay and the pavement on the
right is a 2 inch thick overlay of asphalt-rubber.
A-R Cracks Less
 The
Arizona Department of Transportation has been using the material
since the 1980s. A chart provided by ADOT shows that after ten
years of performance in the field, Asphalt-Rubber resurfacing
not only outperforms conventional resurfacing by 3 to 1, but
it beats out newly constructed pavements as well.
Extensive Research
The Federal Highway Administration's
Turner Fairbank Research Center, Accelerated Loading Facility
located in Northern Virginia near Washington, D.C. has been testing
a variety of modified pavements since 2001. This machine is affectionately
called the "ALF". The machine straddles a pavement
section and rolls a tire, with a specified load, repeatedly across
the pavement surface. While other materials failed, the Asphalt
Rubber (green line, bottom chart) did not crack even  after
300,000 passes! The performance of the Asphalt Rubber exceeds
the most sophisticated chemically engineered asphalt modifiers
available on the market today. Again, this performance was
expected. It reconfirms testing completed in the 1990s.
In 1992, The California Department
of Transportation (Caltrans) and the South African Council for
Scientific and Industrial Research (CSIR) conducted testing with
the Heavy Vehicle Simulator (HVS). Similar to the ALF, the HVS
moves a loaded tire repeatedly over a pavement section a specific
number of times or until it is cracked. After each set of passes,
the cracks are marked and measured.
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 The
Heavy Vehicle Simulator and close up of loading wheel can be
seen in the photos to the right. In this testing, three resurfacing
strategies were studied: A 3 inch overlay with regular asphalt,
a 1.5 inch overlay with asphalt-rubber and a 1 inch overlay with
asphalt-rubber. The testing wheel was loaded to standard weights
expected on U.S. Highways. After 175,000 passes, the Conventional
material had cracks and the asphalt-rubber sections had none.
The wheel load was increased to double the standard wheel load
on U.S. Highways and the testing continued. After 25,000 passes
with double the weight, the conventional, 3 inch section was
completely cracked after 200,000 passes.
For the asphalt-rubber sections,
the testing continued. The very thin, 1 inch AR overlay lasted
for another 37,000 double load passes before it was completely
cracked. But for the 1.5 inch A-R section, the testing continued,
but with the surface temperature of the pavement reduced to 23
degrees. Even in freezing temperatures with twice the load, the
AR resisted cracking. At the final pass, after 250,000 passes
(75,000 passes at double the load) The asphalt-rubber was only
cracked through half of the section.
 The
chart to the left summarizes the test results. The photo to the
right shows the cracks in each section after the testing was
completed. This performance has prompted the Caltrans Chief Engineer
to state in a memo to all Caltrans District Engineers that Asphalt-Rubber:
"..is more durable, resistant to cracking and can achieve
the same service life at half the thickness of conventional dense
graded asphalt concrete for rehabilitation projects. The strategy
improves pavement performance, saves valuable resources and reduces
the number of tires entering landfills and stockpiles."
January 31, 2005, Richard Land, Chief Engineer.
Choose proven long term performance, choose asphaltrubber.
For more info:
www.rubberpavements.org/longtermperformance
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