Roads from plastic waste

The debate on the use and abuse of plastics vis-a-vis

environmental protection can go on, without yielding

results until practical steps are initiated at the grassroots

level by everyone who is in a position to do something

about it. The plastic wastes could be used in road

construction and the field tests withstood the stress and

proved that plastic wastes used after proper processing

as an additive would enhance the life of the roads

and also solve environmental problems. The present

write-up highlights the developments in using plastics

waste to make plastic roads.

Plastic is everywhere in today’s lifestyle. It is used for

packaging, protecting, serving, and even disposing

of all kinds of consumer goods. With the industrial

revolution, mass production of goods started and

plastic seemed to be a cheaper and effective raw

material. Today, every vital sector of the economy

starting from agriculture to packaging, automobile,

building construction, communication or infotech has

been virtually revolutionised by the applications of

plastics. Use of this non-biodegradable (according to

recent studies, plastics can stay unchanged for as long

as 4500 years on earth) product is growing rapidly and

the problem is what to do with plastic-waste. Studies

have linked the improper disposal of plastic to problems

as distant as breast cancer, reproductive problems in

humans and animals, genital abnormalities and even a

decline in human sperm count and quality. If a ban is

put on the use of plastics on emotional grounds, the real

cost would be much higher, the inconvenience much

more, the chances of damage or contamination much

greater. The risks to the family health and safety would

increase and, above all the environmental burden would

be manifold. Hence the question is not ‘plastics vs no

plastics’ but it is more concerned with the judicious use

and re-use of plastic-waste.

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. When mixed

with hot bitumen, plastics melt to form an oily coat over

44 The Indian Concrete Journal NOVEMBER 2008

Point of View

the aggregate and the mixture is laid on the road surface

like a normal tar road.

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.

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. Already, a kilometrelong

test-track has been tested in Karnataka using this

technology. The government is keen on encouraging the

setting up of small plants for mixing waste plastic and

bitumen for road construction. 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.

Developments

The office of the chief minister, New Delhi has

a given a green signal to a private company for

supply of bitumen mixed with plastic which is

used for construction of roads.

The company has already constructed a two-km

road in Bangalore with bitumen mixed with

plastic.

The government of Karnataka was pleased by

the success of the experiment and the state chief

minister himself inaugurated the field test of

construction 500 m of road in three places in and

around Bangalore with the help of PWD using

the innovative technology.

Views

The director of the Central Road Research Institute

(CRRI) said that bitumen mixed with plastic or

rubber improves the quality and life of roads.

The deputy director of the CRRI said that

polymers mixed with bitumen increased the

construction cost up to six per cent, but increased

the longevity of roads manifold.

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.