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Cities reduce maintenance
budgets with CRM asphalt paving programs - a tale of two cities
Throughout the U.S., more and more
cities are finding that their maintenance budgets can be reduced
with a variety of paving strategies using crumb rubber modified
asphalt. The two cities spotlighted in this article have been
using the material for many years, long enough for them to appreciate
the maintenance-free benefits it provides as well as its diversion
of old tires from landfills and smoother riding surface.
Both cities are located in the deserts of the Southwest and are
famous winter vacation spots. One is noted for the colorful characters,
celebrities, and mayors it attracts. The other for some famous
(and infamous) politicians, one credited with being the father
of "conservatism" and making the saguaro cactus and
horn-rimmed glasses a national symbol in 1964.
In case you haven't identified our subject cities, they are Palm
Springs, California and Phoenix, Arizona. Both cities have paved
enough lane miles with old tires to qualify for an Al Gore environmental
award.
Palm Springs
The city started using asphalt-rubber
in 1981. Since 1987 its use has been a vital part of the Palm
Springs pavement maintenance system. The strategy chosen for
residential streets is a process called "Cape Seal,"
which consists of an asphalt-rubber chip seal covered with a
type 11 slurry.
The first phase of their rehabilitation program covered 13 lane
miles. In 1990, 56 more lane miles were covered with the asphalt-rubber
chip seal without a slurry surface. That year, the city started
using the asphalt-rubber hot mix (ARHM) in a two-layer system
in which a 1 1/4-inch ARHM overlay was placed over an asphalt-rubber
chip seal interlayer.
The strategy is used on the arterial streets in the city 1990
was also the year that the I've Got You, Babe biker-mayor
Sonny Bono, now a member of Congress, was so impressed with his
city's streets that he donned more conventional garb and flew
to Washington, DC to testify before the Senate during its consideration
of the Energy Production and Conservation Act of 1990, dealing
with tire recycling credits.In his testimony, Bono praised asphalt-rubber
as having superior engineering and environmental qualities and
for being extremely cost effective.
"Asphalt-rubber technology
is probably the most viable recycling option for used tires"
Mayor Sonny Bono
August 2, 1990
In a 1992 interview, Tom Cartwright, Palm Springs Public
works Inspection Supervisor, said, "We just slurried our
first A-R cape seal ... so we got a good ten years out of it
with no maintenance. We've put down over 100 miles of asphalt-rubber
cape seal since 1991 and we can see the difference in our maintenance
budget.
"Palm Springs is the oldest city in
the area, but it definitely has the best streets. Like most cities,
our maintenance budget gets cut when times are hard. If it hadn't
been for the A-R cape seals and their extended life, we'd be
in real trouble."
Phoenix
This city's experiences with asphal-trubber
probably exceeds that of any agency in the U.S. This is the town
where the late Charles McDonald literally "cooked"
(reacted) a scrap tire rubber and asphalt material in his lab
and created a "band-aid" patch for potholes.
Application methods were extremely primitive in those days as
equipment had yet to be designed to handle this viscous material.
This didn't deter the pioneers in the Phoenix Public Works department.
They worked with contractors and equipment builders until they
had a budding industry in Arizona. In 1964, they placed 140 test
sections of the A-R chip seals. The following year they started
field tests at Sky Harbor International Airport.
The success of these tests was so positive that they launched
a full scale project to seal coat the main taxiway in 1967.
As a result of the excellent performance at the airport, the
city began treating its streets with A- R chip seal on a routine
basis. By 1989, they had placed over 1,000 lane miles of A-R
seals.
But the effort was discontinued after a publicity war was launched
by a radio talk show host that produced a public outcry against
the process. This forced the city to develop an alternate surface
treatment that was as reliable as the A-R chip. The alternative
was a special A-R hot mix.
In the final report of a20-yearstudy, Phoenix engineers concluded
that 12 to 17 years of maintenance-free life could be expected
from the A-R chip seals, more than twice the lifespan of a conventional
chip seal over a sound pavement and seven times that of a seal
over a very poor pavement.
Today, well over 4,000 lane miles of Phoenix streets are A-R
chip seals or hot mix. With extensive use spanning over 30 years,
the city has developed considerable experience with asphalt-rubber
pavements. It has seen a reduction in maintenance budgets and
recycled several million scrap tires in the process.
Information on the city's experience can be obtained in the report
a 20-year study of Asphalt- Rubber Pavements in the City of
Phoenix, Arizona, which is available from the RPA office.
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