28-05-2012, 10:26 AM
Roads from plastic waste
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Plastics roads
Plastic use in road construction is not new. It is already
in use as PVC or HDPE pipe mat crossings built by
cabling together PVC (polyvinyl chloride) or HDPE
(high-density poly-ethylene) pipes to form plastic
mats. The plastic roads include transition mats to ease
the passage of tyres up to and down from the crossing.
Both options help protect wetland haul roads from
rutting by distributing the load across the surface. But
the use of plastic-waste has been a concern for scientists
and engineers for a quite long time. Recent studies in
this direction have shown some hope in terms of using
plastic-waste in road construction i.e., Plastic roads.
A Bangalore-based firm and a team of engineers from
R. V. College of Engineering, Bangalore, have developed
a way of using plastic waste for road construction. An
initial study was conducted in 1997 by the team to test
for strength and durability. Plastic roads mainly use
plastic carry-bags, disposable cups and PET bottles
that are collected from garbage dumps as an important
ingredient of the construction material.
Basic process
Waste plastic is ground and made into powder; 3 to 4 %
plastic is mixed with the bitumen. Plastic increases the
melting point of the bitumen and makes the road retain
its flexibility during winters resulting in its long life. Use
of shredded plastic waste acts as a strong “binding agent”
for tar making the asphalt last long. By mixing plastic
with bitumen the ability of the bitumen to withstand
high temperature increases. The plastic waste is melted
and mixed with bitumen in a particular ratio. Normally,
blending takes place when temperature reaches
45.5°C but when plastic is mixed, it remains stable even
at 55°C. The vigorous tests at the laboratory level proved
that the bituminous concrete mixes prepared using
the treated bitumen binder fulfilled all the specified
Marshall mix design criteria for surface course of road
pavement. There was a substantial increase in Marshall
Stability value of the BC mix, of the order of two to three
times higher value in comparison with the untreated or
ordinary bitumen. Another important observation was
that the bituminous mixes prepared using the treated
binder could withstand adverse soaking conditions
under water for longer duration.
Comparison
The durability of the roads laid out with shredded plastic
waste is much more compared with roads with asphalt
with the ordinary mix. Roads laid with plastic waste mix
are found to be better than the conventional ones. The
binding property of plastic makes the road last longer
besides giving added strength to withstand more loads.
While a normal 'highway quality' road lasts four to five
years it is claimed that plastic-bitumen roads can last
up to 10 years. Rainwater will not seep through because
of the plastic in the tar. So, this technology will result
in lesser road repairs. And as each km of road with an
average width requires over two tonnes of polyblend,
using plastic will help reduce non-biodegradable waste.
The cost of plastic road construction may be slightly
higher compared to the conventional method. However,
this should not deter the adoption of the technology as
the benefits are much higher than the cost.
Conclusion
Plastics will increase the melting point of the bitumen. The
use of the innovative technology not only strengthened
the road construction but also increased the road life
as well as will help to improve the environment and
also creating a source of income. Plastic roads would
be a boon for India’s hot and extremely humid climate,
where temperatures frequently cross 50°C and torrential
rains create havoc, leaving most of the roads with big
potholes. It is hoped that in near future we will have
strong, durable and eco-friendly roads which will relieve
the earth from all type of plastic-waste.