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Thursday, September 26, 2019

Why Waste Plastic Composite Roads are Better than Bitumin Roads Alone

India has built one lakh kilometres of roads in at least 11 states using discarded plastic. 

Plastic-bitumen composite roads have better wear resistance than standard asphalt concrete roads. They do not absorb water, have better flexibility which results in less rutting and less need for repair. Road surfaces remain smooth, are lower maintenance, and absorb sound better.

Roads constructed using waste plastic are durable against extreme weather conditions, are cost-effective and pothole-resistant says World Economic Forum.

The plastic tar roads in Chennai have not developed any potholes, rutting, raveling or edge flaw, even though these roads are more than four years of age, read a performance report by India’s Central Pollution Control Board.

Adding flexible materials to strengthen tar roads is not a new idea. Commercially made polymer-modified asphalts first became popular in the 1970s in Europe. Modified asphalts are made from virgin polymers and sometimes crumb rubber (ground tires).

Polymerized asphalts also tend not to buckle in extreme heat the way conventional roads do – plastic roads will not melt unless the temperature goes beyond 66C, compared to 50.2C for ordinary roads – and are frequently used on roads in the Middle East.

But even in the US, cost is a significant barrier. The most widely used polymer, styrene-butadiene-styrene, can increase the price of a road by 30-50%. In India, high-stress roads like runways and expressways are increasingly using polymer modified asphalts made by manufacturers like DuPont. 

While polymer roads in the US are made with asphalt that comes pre-mixed with a polymer, plastic tar roads are a frugal invention, made with a discarded, low-grade polymer. 

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