How plastic waste can be used effectively in roads

How plastic waste can be used effectively in roads

Whether it is Mumbai, Delhi or Bengaluru, the annual arrival of monsoon brings along with it the glaring issue of potholes. Between 2013 and 2017, the country has recorded 14,926 deaths because of pothole accidents. In more recent numbers, 4,775 road accidents in 2020 were from potholes and 2021 saw...

Whether it is Mumbai, Delhi or Bengaluru, the annual arrival of monsoon brings along with it the glaring issue of potholes. Between 2013 and 2017, the country has recorded 14,926 deaths because of pothole accidents. In more recent numbers, 4,775 road accidents in 2020 were from potholes and 2021 saw about 3,565 accidents. It is also around this time that authorities scramble to, quite literally, plug the issue. In a more serious case, an expressway recently caved in under the heavy rains, a mere five days after its grand opening. “It is a sorry state of affairs,” says Dr Rajagopalan Vasudevan, Professor of Chemistry, Thiagarajar College of Engineering, Madurai.“We need to understand that science is not the issue here. Science cannot fail. A bitumen road can last three to five years without any issues if it is laid correctly. Ideally, the bitumen must be heated to 160°C, mixed and then laid at 110°C. In this case, a plausible case could be that they heated up the bitumen to 200°C because it becomes more watery. But at the first sign of rain, it will get washed away. Here, it is the mistake of the people laying the road, not the science.” Widely known as the ‘Plastic Man of India’, Dr Vasudevan is credited with developing the innovative method of using plastic waste in road construction. Working under the motto of “Plan, Don’t Ban”, the Padma Shri awardee has been developing the use of plastic in various areas such as tiles, sanitaryware, in toilets, ‘plastone’ (plastic-stone) blocks, and many more. He shares more on the process, application and benefits of using plastics as an alternative to road construction. The process India has 46 lakh km of roads. To convert all these roads into plastic-made roads, I need 250 lakh tonne of plastic and India produces about 10 lakh tonne. The entire process can be broken down into four parts: collect it, cut it, dry it and use it. The process itself is quite easy and doesn’t require any high-tech machinery. Before being heated to about 170° C, which is hot enough to melt the waste, the shredded plastic waste is first scattered over a mixture of crushed stone and sand. It is then covered in a thin layer of the melted plastics. The mixture is finished by adding heated bitumen on top, which helps the aggregate to solidify. Carry bags, disposable cups, multilayer films that are difficult to recycle, polyethylene and polypropylene foams, and many other types of plastics can be added to the mix. These materials don't need to be sorted or cleaned before shredding. Durability Plastic is a non-degradable material. I have developed a ‘plastone’ block that is 10 times stronger than concrete. Any structural material can be made stronger with the addition of plastic, as a binder, to it. Normally, the stone is heated to 170°C, bitumen is heated at 160°C and the road is laid. All done. But the problem nowadays is that all roads are laid straight across, allowing water to stagnate. This stagnated water seeps into the road and washes away the bitumen, leading to stones coming out when the road is travelled on. Now, plastic is water-resistant. The science is quite simple: plastic when melted acts as a perfect binder; so, we add the melted plastic between the stone and the bitumen that will then hold both in place and not allow the water to penetrate. No water seepage, no potholes. The life of the road has increased from three to five years to 15 years of pothole-free, maintenance free roads. In addition to life, the road can withstand greater loads than a bitumen road. When plastic is melted and mixed with bitumen to be used in roads, the binding of these materials is so strong that the plastic will not come up, and so the issue of microplastics is also eliminated. Affordability If you want to lay a single lane road of 1 km, typically you would use 10 tonne of bitumen. Per tonne of bitumen costs about Rs 60,000-65,000. If plastic were to be used in this road, you would use 1 tonne of plastic to 9 tonne of bitumen. Plastic waste only costs anywhere between Rs 5,000-10,000 per tonne. So, for every kilometre of road, you are saving Rs 50,000-60,000. On the flip side, the lifecycle of the road is 15 years, so you would also end up saving on maintenance. If the availability of plastic is a gap, the stone can be coated in plastic and made readily available. This gap can also be filled with a new business opportunity. Government initiatives The Government has been very receptive to these methods. The IRC codes outline how to lay plastic in roads. In 2015, the Government made it mandatory to use plastic in roads within 50 km of areas with a population of over 5 lakh. Since then, India has built about 33,000 km of plastic roads. Karnataka and Mumbai have been doing plastic roads. In 2019, a road was built in Meghalaya. The concerned authorities had everything ready and said they could only do the work at night owing to daytimetraffic. Fortunately for me, the operator was a Tamilian and I was able to communicate everything effectively! He learnt everything, went back and laid the road. The road turned so well that they passed on the message to the Prime Minister’s Office. I had the chance to meet the PM and was awarded with the Tech-Icon Award in 2015 and a Padma Shri in 2018. Following these footsteps, the districts of Lei and Kargil have taken the initiative to lay down roads that have at least 10 per cent plastic. The Central Road Research Institute (CRRI) has already organised training for engineers, the Border Roads Organisation (BRO) and National Highways and Infrastructure Development Corporation (NHIDCL). In 2020, the Prime Minister also mentioned that all highways would be made with plastic. And in 2022, the Finance Minister allotted Rs 190 billion to developing rural roads. The main gap lies in the segregation of plastic. If that is done properly, even municipalities can earn by selling this waste to the construction industry. Creating a payback system is very important because everyone cares about the cost more than the sustainability. In the future The government has been quite responsive; I have even given my patent to them but it all comes down to the execution of these plans. When the material is so beneficial to the industry, why not use it? Plastic is a diverse material in its application. I have even developed tiles made of plastic and granite waste. The plastone blocks can be used as pavers. Coat the breakwaters on the seashore with plastic and it will prevent erosion. I am also working on a plastic product for railways. This is the most effective way to manage plastic waste. The pothole problem While it is easier to incorporate plastic into new roads, what about existing ones? Every monsoon brings the plague of potholes. Dr Vasudevan highlights a simple solution to repair them. “I was contacted by an engineer who asked me for a solution for newly emerged potholes after the recent rains,” he shares. “It is not possible to follow the usual method of laying plastic. So, I suggested that they coat the stones with plastic beforehand. Whenever a pothole arises, they can just lay the stones down and pour hot bitumen on top and roll it. This even gives the authorities an opportunity to prepare for the future and have an at-hand, quick solution.” He adds that this method will last for two to three years.

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