No longer the road less travelled

Plastic remains one of the most discussed wastes. According to data released by the Central Pollution Control Board, in 2016 the country generated around 15,342 tonnes of plastic waste daily, of which, 9,205 tonnes was reported to be recycled. The remaining 6,137 tonnes was left littered or uncollected.

Despite several attempts to decrease the use of plastic by legislation, it has clearly not happened. And though, over the years, several States have declared a blanket ban on plastic, none of them can boast of much success.

It is to combat this pollution by plastic that Rajagopalan Vasudevan, Professor of Chemistry at Thiagarajar College of Engineering, Madurai came up with the idea of using waste plastic, along with bituminous mixes, for road construction.

“There are more than 7,000 plastic manufacturing companies in Tamil Nadu alone, so banning plastic is not an ideal solution,” he says. He zeroed in on a new technology that is now being used for the construction of over one lakh kms of road in 11 states. In 2015-2016, the National Rural Road Development Agency laid around 7,500 km of roads using plastic waste. Vasudevan developed the technology in 2002. His experiment of mixing waste plastic with heated bitumen and coating the mixture over stone proved positive. He used the formula to construct a road inside his college the same year. The road proved to be strong and is still in use.

What does the technology entail? Plastic wastes such as carry bags, cups, thermocole, foam and flexible film are shredded into sizes between 1.6mm and 2.5mm. The granite stone is heated to around 170°C and the shredded plastics waste is added to it. The mixture that arises gets coated over stone in just 30 seconds. Bitumen is then added and the mix is used for road construction, even as the road is laid at temperatures between 110°C and 120°C. The process can also be carried out using a central mixing plant. “It helps to have better control over the temperature and better mixing for a uniform coating. All types of roads including national highways can be laid using this technology,” says Vasudevan, also known as the ‘Plastic Man of India’.

The professor received a patent for his technology in 2006. He is also receiving favourable responses from State Governments. Legislation too sided with him, and in November 2015 the Centre made it mandatory to use waste plastic, along with bituminous mixes, for road construction.

Of course, along the way Vasudevan has faced several hiccups. Some environmentalists felt roads built with plastics are not a solution, but a source of pollution. They argued that plastics release toxic gases when heated, so it is harmful to the environment.

Vasudevan refuted these allegations. “The plastic materials used in this technology are getting softened around 140oC without releasing any gas,” he says. “They decompose to release gases only when they are heated beyond 270oC. Our working temperature is only 170oC. We never go beyond this temperature. Therefore there is no question of any gas release.”

On the problem of photodegradation, which causes plastics to break down when exposed to environmental factors such as light and heat, the professor explained that plastic coated over stone interacts with the hot bitumen and gets diffused. There is no separate existence for the plastic anymore. Neither light nor heat affects it. In fact, the bleeding is reduced.

Vasudevan emphasises that the road construction process is eco-friendly, with no toxic gas releases. It is also cheaper to construct as the technology can save around 10 per cent of bitumen. “It doubles the strength of roads and controls wear and tear to a large extent. The roads will last more than 10 years without any maintenance,” he claims.

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