Dr. Ambika Behl - Senior Principal Scientist at CSIR-CRRI, New Delhi
In India, almost 16.5 million tons of plastic is being consumed annually, in which 60% is recycled and the remaining 40% is littering the environment. There is, therefore, an urgent need to utilize the plastic waste effectively with technical developments for plastic reuse and application.
Plastic accounts for 8% of the total solid waste generated in the country annually, with Delhi producing the largest quantity, followed by Kolkata and Ahmedabad, as per a 2018 report by The Energy and Resources Institute (TERI), citing data from India’s Central Pollution Control Board (CPCB).
India generates nearly 26,000 tons of plastic waste every day, making it the 15th biggest plastic polluter globally. Discarded plastic waste litter the country’s roads, rivers, and adds to the huge mounds of garbage dumps. According to CPCB, of the 26,000 tons of plastic waste generated, 94% is thermoplastic, or recyclable materials such as PET (polyethylene terephthalate), and PVC (polyvinyl chloride). These materials can be recycled 7-9 times, after which they have to be disposed off. Waste plastic, mainly used for packaging, is made up of PE, PP, PS.
Innovative use of plastic waste as a bitumen modifier in roadsThe use of plastic waste as a bitumen modifier in roads (referred to as plastic roads), has emerged as an innovative technology, wherein plastic waste is used to modify bituminous mix (8-10 percent by weight of bitumen). The plastic waste has to pass quality standards and undergo sorting, decontamination, shredding, and washing, prior to its mixing with aggregate at the asphalt plant (as per IRC SP 98:2020).
Apart from solving the problem of waste disposal, addition of waste plastics in bituminous mix results in reduction in consumption of bitumen, resulting in overall cost reduction.
Plastic roads have shown to be more durable, resilient, and flexible than conventional bitumen roads, and according to the World Economic Forum, they have proven to be three times stronger than conventional bituminous roads, and have greater resistance to rutting and moisture damage.
ChallengesBitumen is used as a binder for road construction; however, the performance of these bituminous binders is questioned time and again, given that they are brittle and hard in cold environments and soft in hot environments.
An improvement in the property of the binder is the need of the hour. It has been recognised that the deficiencies of bitumen can be overcome by the addition of polymers for improving the visco-elastic behaviour, besides maintaining its own advantages. The addition of polymers typically increases the stiffness of the bitumen and improves its temperature susceptibility, but the addition of fresh/virgin polymers doubles up the bitumen cost and increases the total cost of road construction.
Plastic roads a boon for IndiaThe generation of waste plastics is increasing day by day. It is a common sight in India to find empty plastic bags and other types of plastic packing material littered on roads and choking drains. Due to the impermeability of plastic and its non-biodegradability properties, plastic causes stagnation of water and associated hygiene problems, besides reducing the fertility of the land.
The major polymers, namely polyethylene, polypropylene, and polystyrene show adhesion property in their molten state. Since plastic increases the melting point of bitumen, the use of waste plastic for pavement construction is one of the best methods for easy disposal of waste plastic. Using this innovative technology has proven to not only strengthen road construction but also increase road life, besides creating a source of income.
The increase in high traffic intensity, plying of commercial vehicles on roads, and the significant variations in daily and seasonal temperatures, lead to damaged or potholed roads year after year.
Plastic roads can be a boon for India’s hot and extremely humid climate, where temperatures frequently cross 50°C, and torrential rains create havoc, leaving most of the roads with potholes. With the use of waste plastic in roads, it is expected that we can have stronger, more durable, and eco-friendly roads, plus it will relieve the country from all types of plastic waste. In order to make use of this technology, there must be efficient planning and an effective waste management system.
Advantages of using waste plastic in making roads
- Stronger roads with increased Marshall Stability Value.
- Better resistance towards moisture susceptibility.
- Increased binding and better bonding of the mix.
- Reduction in pores in aggregate and hence less rutting and ravelling.
- High resistance to temperature susceptibility.
- Strength of roads is increased by 100%.
- For 1km X 3.75m roads, 1 ton of plastic (equivalent to 10 lakh carry bags) is used.
- Value addition to waste plastic.
- Cost of road construction is decreased.
- Maintenance cost of plastic roads is less in comparison to control roads.
- Disposal of waste plastic will no longer be a problem.