The Process of Making Composite Plastic Roads

A city’s plastic waste is put through three tasks – cleaning, drying and shredding. The plastic waste can include anything from sweet wrappers to shopping bags.

Once all the plastic waste is shredded (a technique where all the dust particles are eliminated, and plastic items are shredded into fine pieces) these are heated at 165°c. Next, the shredded pieces are added to bitumen mix, which is also heated at 160°c. The final mix is used for constructing roads.

The inventor of the process, Vasudevan melts shredded plastic over low heat to avoid emissions (Dr Vasudevan was honoured with one of India’s highest civilian awards, the Padma Shri, for his groundbreaking research on re-using waste plastic). Polystyrene is toxic when burned but, when softened, it makes an excellent pothole filler.

“Depending on the quality of tar, a 10-30 per cent of it is replaced with the waste plastic. Since both, tar and plastic are petroleum products they gel well together,” said Asad Warsi, Swachh Bharat Mission Consultant, Indore Municipal Corporation.

Every kilometer of a plastic tar road uses the equivalent of 1 million plastic bags, saving around one tonne of asphalt and costing roughly 8% less than a conventional road. 

In experiments to find uses for discarded plastic, Dr. Vasudevan found that in a molten condition, plastic had the property of an excellent binder. Acting on the principle that like attracts like, Dr Vasudevan looked at another chemical of similar nature: bitumen, a black tarry substance that was being combined with gravel to lay roads.

“Bitumen, a highly heterogeneous mixture of hydrocarbons is in effect, composed of polymers similar to plastic,” he says. When molten plastic was added to stone and bitumen mix, Dr Vasudevan found that, true to its nature, plastic stuck fast and bound both materials together.

The bitumen-modified plastic improved the tensile strength of the road by making it more durable and flexible. Plastic also prevented pothole formation. When the layer of molten plastic filled the space between the gravel and bitumen it thwarted rain water from seeping in and causing structural defects.

When late Dr Abdul Kalam, India’s former president and scientist visited Thiagarajar College, he encouraged Dr Vasudevan to lay the first plastic paved road within the campus. In 2002, he paved a 60-ft road within the campus with plastic-modified bitumen. The road is still intact in 2018.

In 2013, The Indian Road Congress developed Guidelines for the use of waste plastic in hot bituminous mixes (dry process) in wearing courses.

The guidelines state that studies have revealed that waste plastics have great potential for use in bituminous construction as its addition in small doses, about 5-10%, by weight of bitumen helps in substantially improving the Marshall stability, strength, fatigue life and other desirable properties of bituminous mix, leading to improved longevity and pavement performance. The use of waste plastic thus contributes to construction of green roads.

Only plastic conforming to Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE), PET and Polyurethane shall only be used in pavement construction.

Plastic Roads will change India

Types of waste plastic usable in road making

The technology for using waste plastics in tar roads has been developed by Dr. R Vasudevan and his team in Madurai, Tamil Nadu at the Thiagarajar College of Engineering. His contacts are given in the video description. 

50 percent of all plastic waste in India is used for packaging which is particularly amenable for road making. Multi-film sachets, foils, PU foam, thermocol can all be shredded and used together in bitumen roads. 

How plastic roads are made

For Normal roads, bitumen is added to heated stone and laid on the surface of the road space. For plastic roads, shredded waste plastic is added to heated stone such that the plastic melts and forms a layer on the stone. Bitumen is then added to this mixture which is then laid on the surface of the road space. The plastic acts as a strong binder between stone and bitumen. Such a road is nearly twice as strong as a normal road and highly durable. Water does not penetrate inside and peel away the bitumen like in normal roads. 

Government support to plastic roads

The first plastic road was laid in Tami Nadu in 2002.  By now, 20,000 kms of rural plastic roads have been laid in Tamil Nadu. The National Rural Roads Development Agency uses this process  to make 5000 kms of roads in India a year. A Government of India notification of Nov 9, 2015 directs that plastic roads will be laid in all urban areas wherever population exceeds 5 lakhs. 

Indian Roads Congress SP 098 of 2013 details the use of waste plastic in hot bituminous mixes (dry process) in wearing courses.

In Plastic Roads, one-tenth of bitumen is saved per km - worth about Rs. 50,000. We are able to use 1 ton of waste plastic per km of plastic roads - that equates to 10 lakh thrown carry-bags ! 

The 40 lakh kms of roads in India can use up all our waste plastic. Only 20 % of Indian roads are black-topped and there is huge scope for improvements in road transport infrastructure using the plastic roads technology. 

Much better pothole repairs too can be achieved by adding 3-5 % shredded thermocol to hot bitumen.

Scientific instruments used to test the process

The road in this video looks like it may have been built just six months ago. But it was actually built in 2002 ! It employed a process where shredded waste plastic substituted  for 10 % of the bitumen. Multifilm, foil, all types of waste packaging plastic can be used for making such a road after shredding into 2-4 mm sized pieces. PU Foam, which today forms a large component of packaging, can also be shredded and added. So can thermocol. 

The Chemistry lab at Professor Vasudevan's department has acquired machines which assisted in the development and testing of this process. 

These machines include the compression testing machine, a marshall stability value testing instrument to test stability of roads, a bitumen penetrometer to test bitumen, etc. 

There is also a computer lab of the chemistry department which has instruments like the thermo gravimetry analyzer, differential scanning calorimeter, optical flouroscent microscopy, fourier transformed infra red spectroscopy, brook field viscometer, etc. 

A patent has been awarded to the Thiagarajar College of Engineering for the plastic roads process.

Smart india needs smart roads

The technology for the use of plastics in road has been developed by an Indian, in India, for use in India. 

The Tamil Nadu Government set up self-help groups in every district to gather plastic packaging wastes. The Government has given loans to such self-help groups to purchase shredding machines. They shred the collected plastic and keep it ready for the Government to purchase such plastic from them for road making. 

This technology can help make the best use of scarce fossil fuel resources and waste plastic packaging that currently clogs up India’s water channels and spoils our land. 

Smart India needs Smart Roads. Smart Roads can be made by adding waste plastic to them. So waste plastic packaging can be a useful resource for India as long as it is kept segregated, collected and stored at a central place for shredding and adding to roads. If the home and its surroundings are clean of plastic packaging waste, the city is that much cleaner. 

Every citizen who complains of a dirty street or a dirty country can begin in their home with keeping their dry waste separate and giving it separate.