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Concrete in the Transit Industry
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Concrete in the Transit Industry
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Intermodal facilities are catalysts
to public transit growth. |
The transit industry is in a unique position to help the environment
by using concrete for foundations, piers, columns, guideways, station
and maintenance facilities, platforms, crossties, slab track, grade
crossings, parking facilities, retaining walls, and pavements. Specific
elements of structures used within the transit industry have additional
environmental benefits.
• Transit maintenance facilities, stations, and buildings
that are constructed of concrete are energy efficient, easier
to cool and heat, and save money by reducing temperature swings.
A concept called Fabric Energy Storage (FES) uses the thermal
capacity of the building fabric to attenuate and delay peak internal
temperatures during the occupied period. In the summer, heat is
absorbed and stored in the building structure, and is then released
at night. Peak internal temperatures can be reduced by approximately
9 °F (5 °C).6
• Pavements for intermodal facilities and parking lots,
and garages constructed of concrete can cash in on concrete’s
natural reflectivity, resulting in reduced lighting requirements
and energy savings. It has been shown that the number of street
lights can be reduced by one-third if pavement is constructed
of concrete.7
• Pavements, platforms, and facilities constructed of concrete
can help lower temperatures of “urban heat islands,”
thereby saving energy and money. The U.S. Department of Energy
and the U.S. Environmental Protection Agency estimate that on
warm summer days, the air in a city can be 6 to 8 °F (3 to
4 °C) hotter than the surrounding countryside, thus creating
higher demands for energy. Research on the city of Los Angeles
has estimated that a decrease in temperature of about 3 °F
(2 °C) could result in annual savings of over $70 million.8
In addition, for every degree above 70 °F (39 °C), smog
increases by 3%, and pollution increases by 2%. Temperature rises
are offset by the naturally light color of concrete.
• Bridges and aerial guideways constructed of concrete
have historically fared better than those made of other materials.
Data from the National Bridge Inventory (NBI), which is administered
by the Federal Highway Administration, indicate that reinforced
concrete and prestressed concrete bridges have a significantly
lower rate of structural deficiency compared to steel or timber
bridges.9 Also, reinforced concrete
and precast, prestressed concrete structures are preferred by
owners and engineers for their aesthetics, durability, low initial
cost, low maintenance, and environmental safety.10
• Concrete pavement used for roadways associated with transit
systems or for intermodal and bus facilities benefits the environment
in two ways. First, studies have concluded that the consumption
of fuel by vehicles traveling on concrete pavements decreases
compared to vehicles traveling on other materials. Energy savings
generally increase as the weight of the vehicle increases, although
other factors, such as the number of axles, also affect the resulting
savings. Energy savings as high as 25% were noted.11,12,13
Second, concrete pavements have a lower life-cycle cost because
they are much less prone to experience deterioration and permanent
deformation due to shear strain, compared to asphalt pavements.
Studies have shown that vehicular traffic causes asphalt pavements
to rut and experience other modes of failure not associated with
concrete pavements.14
With annual increases of ridership in public transportation and
recent increases in government funding, the transit industry has
an extraordinary opportunity to make a difference for the benefit
of our environment. Using concrete for transit projects benefits
the environment and provides economical, strong, beautiful, and
durable structures and pavements.
References:
(6) Glass, J., Kendrick, C., and Baiche, B., Opportunities for
Fabric Energy Storage in Concrete, 1999.
(7) Stark, Richard E., “Road Surface’s Reflectance Influences
Lighting Design,” Lighting Design + Application,
April 1986.
(8) Pomerantz, M., and Akbari, H., Cooler Paving Materials for
Heat-Island Mitigation, LBNL, Berkeley, California.
(9) Market Share Analysis of U.S. Bridge Construction,
SR342.01E, Portland Cement Association, 1995.
(10) Measurement Criteria: The Bridge Market 1996, Portland
Cement Association, March 1997.
(11) Zaniewski, J. P., Effect of Pavement Surface Type on Fuel
Consumption, SR289.01P, Portland Cement Association, 1989.
(12) Zaniewski, J. P., Butler, B. C., Cunningham, Elkins, Paggi,
and Machemehl, Vehicle Operating Costs, Fuel Consumption, and
Pavement Types and Condition Factors, Final Report No. PB82-238676,
Federal Highway Administration, Washington, D.C., 1982.
(13) Phelps, R.E., and Mingle, J. G., Pavement and Tire Rolling
Resistance Coefficients for Vehicle Energy Prediction, Department
of Civil and Mechanical Engineering, Oregon State University, pp.
123–132.
(14) “New Trucks for Greater Productivity and Less Road Wear,
An Evaluation of the Turner Proposal,” Special Report
227, Transportation Research Board, National Research Council,
Washington, D.C., 1990.
Selected PCA publications and other resources concerning
environmental issues associated with concrete and the transit industry:
• Environmental Life-Cycle Assessment of Portland Cement
Concrete, PCA Serial No. 2167, 1998.
• Building
a Cleaner Environment, PCA SP337, 1999.
• Cement
and Concrete in the Global Environment, PCA SP114, 1993.
• The Environmental Council
of Concrete Organizations (ECCO), 5420 Old Orchard Road, Skokie,
IL 60077-1083.
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