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 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.
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.
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.
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.