India wakes up to plastic roads

Using plastic wastes for laying roads is fast catching up among Indian cities and Indian government is mulling to formulate national level policy to use the technology on highways roads.

 Though several cities in India have banned usage of plastics, the disposal of a large quantity of non-biodegradable wastes being accumulated daily has become a challenging task for the governments and a worrying factor for environmentalists. Though re-cycling of plastics is addressing the issues to certain extent, it’s still lot to done. Using waste plastic materials to lay roads is a new concept, fast catching up in India.

Tamil Nadu has become a pioneer in using this technology invented by Chemistry professor Vasudevan of Thiagarajar College of Engineering in Madurai. Now, encouraged by the use of plastic in road laying in Tamil Nadu, the Centre is mulling a national level policy on its usage on national highways and other state highway roads. Mumbai too has tested plastics on road laying and found it to be a viable solution for frequent re-laying of roads after every monsoon.

"Using plastic in laying roads will increase the life of roads. We have to prepare a national level policy on this. We are talking over this," Environment and Forests Minister Jayanthi Natarajan told reporters on the sidelines of the seventh national meet of state biodiversity boards here.

Chennai Corporation had launched a programme to use plastic in laying roads.

The National Rural Roads Development Agency (NRRDA) has formulated guidelines for the use of plastic waste in rural roads construction. With the help of research carried by Prof. Vasudevan, Prof. Justo and Prof. Veeraragavan at Bangalore University and research carried out by Scientist at CRRI, New Delhi, NRRDA has built several trial roads using waste plastic.  

Such roads, popularly known as Plastic Roads, are found to perform better compared to those constructed with conventional bitumen. Further it has been found that such roads were not subjected to stripping when come in contact with water. With the experience gained over the years of construction of roads using waste plastic, CRRI as well as TCE have firmed up the specifications for the use of waste plastic and shared the specifications with organizations willing to construct the roads with waste plastic.

The guidelines were formed based on the presentations made by Dr. Sangita, Sr. Scientist, Flexible Pavement Division, CRRI and the literature supplied by Dr. R. Vasudevan.

Types of waste plastic, which can be used in the construction of rural roads can be classified as films, carry bags, cups, hard foams, soft foams, laminated plastics and packing materials used for biscuits, chocolates, etc.

Method of road laying

Dry process is recommended for isolated works. It is recommended that the percentage of shredded waste plastic will be 8% by Central Road Research Institute (CRRI), while the same is specified as 10% by Dr. Vasudevan. However we can adopt 8% as the optimum plastic content for blending the bitumen in the construction of plastic roads. The details of the process are given below. Bitumen of grades 60/70 or 80/100 can be used as binder as in case of conventional method, NRRDA said in a report.

With mini hot mix plant

 

The stone aggregate mix (as per specification) is transferred to the mix cylinder where it is heated to 165⁰c (as per the IRC specification) and then it is transferred to the mixing puddler(Temperature can be monitored using IR thermometer), while transferring the hot aggregate into the puddler, calculated quantity of shredded plastics is sprayed over the hot aggregate within 30seconds. The sprayed plastic films melts and gets coated over the aggregate, thus forming an oily coating.

Similarly, the bitumen is to be heated to a maximum of 160⁰c in a separate chamber and kept ready (The temperature should be monitored to have good binding and to prevent weak bonding).

At the mixing puddler, the hot bitumen is added over the plastic coated aggregate and the resulted mix is used for road construction. The road laying temperature is between 110⁰c to 120⁰c. The roller used is normal 8-ton capacity.

Advantages of plastic roads

·          

A well constructed plastic tar road will result in the following advantages.

·         Strength of the road increased (Increased  Marshall Stability Value)

·         Better resistance to water and water stagnation

·         No stripping and have no potholes.

·         Increased binding and better bonding of the mix.

·         Increased load withstanding property( Withstanding increased load transport)

·         Overall consumption of bitumen decreases.

·         Reduction in pores in aggregate and hence less rutting and raveling.

·         Better soundness property.

·         Maintenance cost of the road is almost nil.

·         The Road life period is substantially increased.

·         No leaching of plastics.