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technologieS
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Use
of Recycled Tire Rubber in Concrete
The Need
More than 250 million scrap tires weighing
more than 3 million tons are generated each year in
the United States (Naik and Siddique 2002). This is
considered as one of the major environmental challenges
facing municipalities around the world because waste
rubber is not easily biodegradable even after a long
period of landfill treatment. One of the solutions suggested
is the use of tire rubber particles as additives in
cement-based materials.
Although concrete is the most popular construction material,
it has some limited properties: low tensile strength,
low ductility, low energy absorption, and shrinkage
and cracking associated with hardening and curing (Wang
et al. 2000). Several studies performed recently showed
application of the recycled tire rubber might improve
these weak characteristics of concrete.
The Technology
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While
rubberized asphalt has been used for decades on
roadways (in fact, Intermodal Surface Transportation
Efficiency Act (ISTEA) set in 1991 mandated the
use a minimum of 5% recycled rubber by weight
of asphalt place and the percent of rubber used
was to increase gradually up to 20% by the year
1997. The mandate was revoked in 1996 (Khatib
et al. 1999)), rubberized concrete is a technology
infant.
Many studies have been performed to investigate
the feasibility of the usage. Since a number of
ways to use the recycled rubber in the concrete
design are possible and there are still many factors
and properties that should be |
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investigated, it may be difficult to expect that mass
production-base rubberized concrete is able to be available
in the market today or next week. However, many study
results have proven the mechanical and environmental
advantages of the use of recycled tire as addition to
cement concrete.
Many experiments were done to find out appropriate methods
of rubber application. Commonly, fully replacing coarse
aggregate (gravel) or fine aggregate (sand) with rubber
is not appropriate because the loss of strength is too
severe. However, with small portion of aggregates replaced,
the loss in compressive strength was not significant.
A research study by Khatib et al. (1999) and Schimizze
et al. (1994) suggested that rubber should not exceed
17-20% of the total aggregate volume. Experiments under
the laboratory environments commonly presented that
the use of rubber in the concrete cement mix reduced
drying shrinkage, brittleness, and elastic modulus,
which might improve the overall durability and serviceability
of concrete cement.
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The
Benefits
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Recycling
of scrap tires suggesting an environmental
solution.
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Reduction
of plastic shrinkage cracking Diminishme
nt of the vulnerability
of concrete to catastrophic failure
Status
Recently, Dr. Zhu (Arizona State University)
tried to apply rubberized concrete in the real
world cases including dozens of residential and
commercial sites. Crumb rubber of 8 percent of
the cement weight was used. |
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Barriers
- Large variation of concrete performance according
to the application method and ratio of rubber usage
- sensitive to variations in procedure (Chung and
Hong 1999)
- Costly procedure of rubber particle preparation
References
- Chung, K., and Hong, Y. (1999). "Introductory behavior
of rubber concrete." Journal of Applied Polymer Science,
72, 35-40.
- Naik, T. R. and Siddique, R. (2002). "Properties
of concrete containing scrap tire rubber - an overview."
UWM CBU Report No. CBU-2002-06.
- Wang, Y., Wu, H. C., and Li, V. C. (2000). "Concrete
reinforcement with recycled fibers." Journal of Materials
in Civil Engineering, ASCE, 12(4), 314-319.
- Khatib, Z. K., and Bayomy, F. M. (1999). "Rubberized
portland cement concrete." Journal of Materials in
Civil Engineering, ASCE, 11(3), 206-213.
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