One to Watch
Another cold climate project by the
COLORADO DOT-Aeronautics Division
Glenwood Springs, Colorado
is an alpine climate hamlet on the western slopes of the Rocky
Mountains situated halfway between its famous neighbors, Aspen
and Vail. The elevation is 5,746 feet and the average annual
precipitation is 16.5 inches. Snowfall is an average 67 inches
in town with much higher precipitation and snow on the nearby
14,000 ft. peaks.
The CDOT-Aeronautics Division, under the leadership
of their Airport Engineer, T.K Gwin, resurfaced the Glenwood
Springs runway with an Asphalt-Rubber Cape Seal* in June, 2003.
The 30,000 sq. yd. project was funded by the Colorado Dept. of
Local Affairs Waste Tire Grant Program, the U.S. EPA Solid Waste
Management Program and the Colorado Discretionary Aviation Grant
program and the City of Glenwood Springs.
In a final construction report issued by the CDOT
Aeronautics Division, the agency said "The validity of rubber
asphalt paving materials had been proven by our sister states
of California and Arizona, which rely heavily on the process
to provide a significant increase in the longevity of the pavement
and the wise recycling of used auto tire products. Reflective
cracking has all but been eliminated with the process and the
pavement remains flexible and viable long after non rubberized
materials have failed."
"In the past, the acute stresses placed on pavements
at high altitude Colorado locations have made it necessary to
rehabilitate airport movement areas every 2 to 3 years. It is
anticipated that the introduction of the rubber asphalt materials
will extend the life of the pavements for 7 to 10 years." |
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Glenwood Springs Municipal Airport
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The CDOT-aeronautics Division will
closely monitor the state of airport surfaces during the anticipated
lifecycle of the pavement. The Division has in place a triennial
pavement condition inspection for all airport surfaces in Colorado,
which provides a means of profiling this pavement as it compares
with past pavement history at the Airport and other airports
with similar climatic conditions." The CDOT Aeronautics
Division briefed the Colorado Airport Operators Association about
the success of the project during its annual conference in Steamboat
Springs in early October. The project utilized more than 4,800
recycled Colorado tires. The Asphalt-Rubber contractor for the
Glenwood Springs Airport rehabilitation was International Surfacing
Systems of Chandler, Arizona.
*Asphalt-Rubber Cape Seal. This consists of an Asphalt-Rubber
Stress Absorbing Membrane (SAM), a chip seal process covered
with a Type II Slurry Seal. The spray application rate of the
SAM binder is generally .55 to .70 gallons per sq. yd. The hot
binder is then covered with hot, pre-coated aggregate at a rate
of 30 to 40 lbs. per sq. yd. This process was developed near
Cape Town, South Africa, hence the "Cape Seal" designation. |
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Nebraska
Three projects on the ground and two
more in the works
The Nebraska Department
of Roads placed its first Asphalt-Rubber project in September,
2001 on Highway 2 near Lincoln. The project consisted of a 1/2
inch to 11/2 inch SP5 leveling course and a 2 inch Asphalt-Rubber
gap graded mix over a heavily deteriorated concrete pavement
that was milled 3/4 inch.
The elevation in the Lincoln area is 1,167 feet,
hardly Alpine climates as the Colorado and Northern Arizona areas,
but definitely cold in the winter. January temperatures range
from a high of 32 to lows of 10 degrees F. The summer temperatures
average in the nineties according to the Chamber of Commerce
and up to 104F if you talk to NDOR. Annual measurable precipitation
is over 28 inches.
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Highway 2 in February 2002, 6 months
after resurfacing with Asphalt-Rubber.
Typical pavement condition on Highway 2 prior
to AR rehabilitation |
| Since the Highway 2, NDOR has placed
Asphalt-Rubber projects on Interstate 80 andHighway 14. According
the NDOR Materials Engineer, Robert Rea, the projects are performing
well. Some cracking has occurred on the Highway 2 project but
Rea reports the DOR had anticipated some cracking as the underlying
concrete pavement was the "worst we could find." (photo)
NDOR, which researched Asphalt-Rubber for three years prior to
its first project, is planning an AR OGFC with lower voids and
a higher binder content as one of its two upcoming projects.
Based on the positive indications of the NDOR Asphalt-Rubber
program, Dobson Brothers, a prominent Nebraska contractor, has
purchased an Asphalt-Rubber blending unit to service future needs. |
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