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Concrete Benefits the Environment
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Concrete Benefits the Environment
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The cement industry continues to modernize
plants and make them more efficient. |
As owners, planners, and designers contemplate the form and function
of new or expanding transit systems, the superiority of concrete
as a construction material becomes evident. The many historic benefits
of concrete are familiar to us all: low first cost and maintenance
costs result in economical projects; high strength produces engineered
elements that can handle loads effectively and efficiently; versatility
is the tool for limitless creativity and aesthetic possibility;
and durability leads to enduring structures that stand the test
of time. These factors in themselves are steadfast reasons for making
concrete the first-choice material. As issues continue to arise
concerning the environment, however, and as transit systems proliferate,
environmentally friendly construction materials are even more desired.
Many environmental attributes of concrete have been documented and
are itemized below.
• Concrete is composed of naturally abundant materials,
including water, stone, sand, and portland cement. Portland cement
itself is manufactured from natural materials including various
combinations of limestone, shale, clay, sand, and iron ore.
• Concrete uses waste products from other industries that
would eventually end up in landfills. Coal burning power plants
generated 63 million tons of fly ash in 1998—with over 10
million tons used in concrete products. The use of fly ash decreases
the leachability, porosity, and permeability of concrete. It also
decreases the potential for thermal cracking by lowering the peak
temperatures during hydration, and greatly reduces expansion and
subsequent deterioration associated with alkali-silica reactivity.
Bottom ash, also a waste product from coal burning power plants,
totaled 17 million tons, of which 5 million tons was used by the
concrete industry. Blast furnace slag is a byproduct of the steel
industry. Concrete uses about 2 million of the 3 million tons
of slag produced each year.1
• Concrete is recyclable. Crushed concrete can be used
as aggregate in new concrete mixes or as a base material for new
pavement, thereby saving energy and valuable landfill space. The
Portland Cement Association estimates that over 100 million tons
of concrete is currently being recycled each year.2
• The cement industry has reduced the amount of energy
needed in cement production by almost 30% since the early 1970s
by closing inefficient plants and modernizing and automating the
remaining plants.3 The cement industry
has also reduced the use of fossil fuels in cement production
by over 25% since 1971.4
• The cement industry uses fossil fuel in its high-temperature
kilns; however, according to the U.S. Department of Commerce,
the cement industry invests 1.8% of its value of shipments into
pollution abatement, compared with 0.23% for manufacturing as
a whole. When the comparison considers total pollution abatement
capital expenditures versus overall new capital expenditures,
manufacturing as a whole invests about 7%, while the portland
cement industry invests over 20% of its capital expenditure dollars
in pollution abatement equipment.5
• The cement industry has steadily increased its use of
waste materials to fuel cement kilns and currently relies on the
burning of waste materials to satisfy about 8% of its total energy
needs.3 Cement plants now burn many
household and industrial wastes that would otherwise go into landfills
or have to be handled as toxic wastes, including scrap tires,
spent motor oil, surplus printing inks, dry-cleaning solvents,
paint thinners, petroleum industry sludge, and agricultural wastes.
References
(1) Kalyoncu, Rustu, Coal Combustion Products,
1998.
(2) Portland Cement Association market research, 1998.
(3) 1998 U.S. and Canadian Labor-Energy Input Survey, Economic
Research department, Portland Cement Association, October 1999.
(4) Portland Cement, Concrete, & PCA, MS330, Portland
Cement Association.
(5) 1994 Annual Survey of Manufacturers: Statistics for Industry
Groups and Industries, Bureau of the Census, U.S. Department
of Commerce, Washington, D.C., 1996.
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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