Synthetic Athletic Field and Track
Missouri Polymer Ambassador: Mary Harris
Since John Burroughs School is having a new football field covered with artificial
turf, it occurred to me that this is an opportunity to explain the history, technology, and
science of artificial fields. It is not cheap to make a conversion from a natural grass field
to a polymer one!
The idea for an artificial turf began in the 1950’s with the Ford Foundation and
Chemstrand Company, a subsidiary of Monsanto Industries. In 1964, synthetic turf was
called Chemgrass and was installed at Moses Brown School in Providence Rhoda Island.
The AstroDome installed Chemgrass which was renamed Astroturf in 1966. Indiana
State University in Terre Haute, Indiana had the first outdoor stadium with Astroturf. In
1967, Astroturf was patented for “monofilament ribbon file product” by Monsanto
Industries. There are many competitors now in synthetic fiber for athletic fields.
Poligras® was used in Sydney for the 2000 Soccer Olympics. Baspograss® is a sandfilled product selected in Germany, France, England, New Zealand and Australia.
Besides athletic fields and tracks, synthetic surfaces are available for tennis courts, indoor
sport surfaces, lawn bowls, in-line skating, golf, residential lawns, playgrounds and
leisure areas.
Our field is just outside the science building so I get a view of the process every
day during the fall. This is our field before the work started in June 2005 with completion
date of October 2005.
Engineers had to design an acceptable drainage system so the neighbors to the school
would approve. Tons and tons of soil were removed and concrete drainage installed. A
filter fabric was put down before rock-fill was added forming a base of 2 feet in thickness
over the field. Artificial turf was rolled and stretched on top of the gravel. The highest
point is the center of the field with a 0.5% slope. Kiefer Speciality Flooring Inc. has
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installed artificial turf at CBC High School in St. Louis, University of Tennessee,
University of Colorado, and University of Iowa.
In the artificial turf diagram,
“A” is the polyolefine fibers of “grass”
(5.5 cm long), “B” is the SBR rubber
granules (post consumer product) held
by the grass fibers, “C” is the sand
layer to lock the fiber in place and
provides stability, and “D” is the 100%
polypropylene backing. The coating
on the backing is latex based on
styrene-butadiene. The lines on the
field are white or yellow grass that
comes in 50, 75 or 100 mm widths.
Prestige System by Kiefer Specialty Flooring, Inc
Close-up of artificial turf with backing.
Density of 9,450 tuffs per square meter.
The back of the turf looks like rug hooking.
There are holes in the backing about every 10 cm.
Once the fine rubber granules are spread on the field, the grass must be fibrillated
with a special machine to even the amount of rubber embedded in the grass surface.
The rubber granules come from recycled tires.
This picture on the right shows the 0.5 mm to
1.5 mm granules next to a dime. Recycling tires
all begins with a tire shredder. A high-speed,
tub-style grinder has a rotating hopper where
scrap ties are placed. As the tub rotates, it places
the tires in contact with rotating hammers or a
hammermill. The tips of each hammer have
carbide cutting teeth which grind the tires into 6
inch pieces or less. A secondary grinder reduces
the pieces to smaller size. The force of the hammers separate the steel wire fragments
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and an in-line magnet removes the steel from the shredded tire. These grinders can
handle up to 4,000 tires per hour.
Hammermill for tires.
Rotary Shear Shredder
The rotary shear shredder or “hook-shear” shredder uses hook-shaped blades to
grab a tire and draw it down through the blades for shredding. The blades are made from
heat-treated steel alloy. These blades can be re-welded and sharpened to fit many
different configurations so the machine can shred wood or any other solid waste. They
cut the waste like giant scissors. (www.americanrecycler.com)
There are many uses for recycled tires. The top three are:
landfill acceptance, tire derived fuel (TDF), and crumb rubber for
hundreds of products. TDF is sold to an industry like a paper mill
where the tire chips are co-mingled with bark and coal to feed giant
boilers. The steam generated from the burning of the fuel powers the
machines in the mill. Crumb rubber is used in septic system fields,
rubber modified asphalt, footwear, barrier walls, erosion control systems, marine
surfaces, livestock feeders, rubberized plastic lumber, railroad ties, and traffic control
products.
A relatively new patent (March 25, 2003 - #6536690) developed by the
Agricultural Research Service (USDA) describes a new method to recycle tires. The
polyester/nylon fiber called fluff is pulverized. In the past, the fiber has been sent to land
fills but with this idea, the fiber would be sent to “cotton ginning technology” to recover
the fiber for reuse in garden hoses, floor mats, brake pads, and carpet backing.
(www.ars.usda.gov/research/patents/patents.htm)
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The base for the track is 4 inches of asphalt. The base must cure and de-gas for
one month before the Mondo Sportflex Super X sport surface was applied. The Mondo
surface is a double layer of rubber construction. The bottom layer provides shock
absorption with its waffle structure and the top (red) layer has an embossed surface for
easy maintenance and excellent traction. The picture on the left shows the bottom layer
on the top of the picture. The picture on the right shows the texture on the top surface.
Mondo by Sportek Surfaces (14 mm thick) (www.mondoworldwide.com)
The Mondo track is not poured onto the asphalt. The product is shipped in rolls to
the site. The raw rubber (not recycled) has a few additives such as pigments for color,
agents to make it harder and denser, and a UV protector. The two layers are produced
separately and later they are vulcanized to stick together. While the material is hot and
soft, the texture is imprinted onto the surface. It is further “cooked” and trimmed to the
correct lane width. Each package is labeled “Lane 1, roll 1” etc. The rolls are applied to
the surface with adhesive. Bricks or weights are placed on the Mondo lanes to help with
a tight bond with the asphalt. Synthetic tracks did not become popular until the 1960’s.
The 1964 Tokyo Games has the last pre-rubber Olympics.
(http://slate.msn.com/id/2105744/)
Mondo tracks were present at:
2004 Athens, Greece
2000 Sydney, Australia
1996 Atlanta, U.S.A.
1992 Barcelona, Spain
1988 Seoul, Korea
1984 Los Angeles, U.S.A.
1980 Moscow, Russia
1976 Montreal, Canada
Other colleges with tracks of this surface are Indiana University, University of
Nebraska, U.S. Naval Academy, Bates College, Duke University, Georgia Tech, and San
Diego State University.
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