Civil Engineering Reference
In-Depth Information
Fig. 2.13 Molecular formula
of polyethylene terephthalate
(C carbon; H hydrogen;
O oxygen; n nos. of
monomers)
[C: carbon H: hydrogen O: oxygen; n: nos. of monomers]
2.8 Waste Tyre Rubber
The tremendous growth of automobile industry and the increasing use of car as the
main means of transportation have increased its production, thus generating huge
amounts of tyre rubber wastes. Extensive research works have been carried out to
find the way to utilise the rubber tyre waste in various applications. Like plastic
wastes, rubber tyre is non-degradable in nature at ambient conditions. This has
generated massive stockpiles of used tyre and is creating huge environmental
problems including fire hazards. Recently many countries have forbidden land
filling of scrap tyres and therefore recycling of this material in the production of
other products has immense importance. Out of several management options, the
use of waste scrape tyre in the production of cement mortar and concrete is a
promising path.
About 300 million tyres were generated in the USA in 2005 and the total
number of scrap tyres consumed in end-use markets reached approximately 260
million (Rubber Manufacturer Association
2006
). About 190 million scrap tyres
remained in stockpile at the end of 2005 in the USA (Rubber Manufacturer
Association
2006
). This is a simple example and if this scenario is considered for
the whole world, the amount of rubber tyres remaining as waste will be increased
manifold.
Ganjian et al. (
2009
) classified tyre rubber into two classes according to the type
of vehicles that use the tyre. The natural and synthetic rubber contents in car tyres
are different from those in truck tyres (Table
2.32
).
According to the use of tyre rubber in concrete preparation, it can be separated
into three types (Ganjian et al.
2009
):
1. Shredded or chipped rubber is used to replace gravel. By shredding the rubber
pieces, particles about 13-76 mm big are produced.
2. Crumb rubber is used to replace sand with size range 0.425-4.75 mm and is
manufactured by using special mills. The size of rubber particles depends on
the type of mill used and the generated temperature.
3. Ground rubber can be used as a filler material to replace cement. The tyres are
subjected to two stages of magnetic separation and screening to produce this
size of rubber particles. In micro-milling process, the rubber particles made are
in the range of 0.075-0.475 mm.
Several studies were made to evaluate the properties of concrete incorporating
recycled tyre rubber as aggregate or filler material. The size, proportion in concrete
mix, and surface
texture of rubber particles affect the strength of concrete
