A government order in November 2015 made it mandatory for all road developers in the country to use waste plastic along with bituminous mixes for construction. This was to help overcome the growing problem of plastic waste disposal in India. The technology for the same was developed by Rajagopalan Vasudevan, the “Plastic Man of India” and professor of chemistry at Thiagarajar College of Engineering in Madurai, Tamil Nadu.
Plastic has slowly become an integral part of all our requirements. Carry bags, packaging material, bottles, cups and various other items once made from other stuff are being manufactured from plastic because of the advantages — it is durable, easy to produce, lightweight, unbreakable, odourless and chemical-resistant.
But plastic does not decompose and that’s its biggest drawback. Plastic waste is commonly seen around the country and often clogs drains, thereby causing floods. It can only be recycled a couple times as melting plastic for the process releases highly toxic fumes. From the turn of this century, a lot of noise has been made to reduce the use of plastic and control the waste it generates.
One evening, Vasudevan saw a doctor on a TV programme saying that plastic “dissolved” in waterbodies and caused pollution. “That set me thinking. Since plastic is a product of petroleum, the doctor&’s theory had to be false. There was a lot of talk about banning plastic products across the country and finding solutions to plastic waste. I decided to take up the challenge and started experimenting to see if I could find a solution,” he says.
Laboratory results of mixing waste plastic with heated bitumen and coating the mixture over stone proved positive. Vasudevan implemented the use of plastic waste on a road constructed inside the premises of his college in 2002. “To date, that stretch of road is still going strong,” he says. In 2006, the Thiagarajar College of Engineering received the patent for this technology.
The items that can be used for road construction are carry bags, cups and packaging material for food products. The process is quite simple. The plastic waste material is first brought down to a particular size using a shredding machine. The aggregate mix is thereafter heated at 165° Celsius and transferred to the mixing chamber, and the bitumen is heated to 160° Celsius for good binding. It is important to monitor the temperature during heating. The shredded plastic waste is then added to the aggregate. It gets coated uniformly over the aggregate within 30-60 seconds, giving an oily look. The plastic waste-coated aggregate is added to hot bitumen and the resulting mix is used for road construction.
“The advantages of using waste plastic for road construction are several. The process is easy and does not need new machinery. For every kilogram of stone, 50 gm of bitumen is used and a tenth of that weight is plastic waste — this reduces the amount of bitumen being used. Plastic increases the aggregate impact value and improves the quality of flexible pavements. Wear and tear will also decrease to a large extent,” explains Vasudevan.
This process of road construction is extremely eco-friendly, with no toxic gases being released, and it can generate job opportunities for rag pickers. Such roads have better resistance against rain and cold. Since a large amount is required for a small stretch of road, the quantity of plastic waste strewn around will definitely reduce.
Vasudevan&’s inclination to keep experimenting led to another innovation. He decided to try and create a stone block with plastic coating and, in 2012, “plastone” was born. A plastone block is made from a mixture of plastic waste and stone. It has been found to withstand more pressure and resists water percolation. In the professor&’s department of chemistry, they have made plastone blocks using granite and ceramic waste, along with plastic waste. Each block consumes 300 carry bags and around six PET bottles. “It is an easier way for disposing plastic bottles,” Vasudevan points out.
Almost 10 per cent of solid waste consists of used materials that can be broken into pieces and used in the making of plastone. Industrial slug can also be used in the process. One of the foremost advantages of plastone is its non-porous nature and the ability to prevent water penetration.
Plastone can be used for flooring, especially outdoors. It can be a cheap and strong substitute for cement blocks, which have a tendency to wither away in constant rain. It can be an effective liner for waterbodies, especially canals, preventing water seepage. It can also be used to raise compound walls. A coat of emulsion can be provided to make it colourful and attractive.
The college, and the professor in particular, have been receiving many queries from various countries in Europe and the Americas for this technology. “Swacch Bharat is our first priority,” says the professor. “We will first help India dispose of its waste material by spreading the message about the use of plastic waste in road construction and usage of plastone. Once we have made headway in almost every part of our country, we will share this technology with other countries.”
The Better India