PLASTIC ROADS: Plastic waste materials are a menace on the streets and in the drainages of Kampala city, despite efforts by some companies to collect and recycle them. Many of these companies export the recycled plastic in form of pellets to China. Some of the plastic waste is either incinerated or land filled.
In a bid to reduce the environmental impacts of road construction including carbon emissions, a number of innovations have been developed, such as the use of recycled plastic waste to replace the bitumen in the asphalt used for road construction.
Traditional road construction needs large amounts of bitumen, cement and crushed rock to strengthen the material and hold the pavement together. Bitumen which is petroleum based, is a highly volatile organic compound whose application releases harmful substances into the atmosphere, negatively impacting the environment. Traditional road construction releases about 96 million tons of carbon dioxide into the atmosphere annually.
To reduce the carbon emissions during road construction, recycled plastics can be shredded into small pellets and added to asphalt during road construction which results in an overall reduction of amount of the bitumen needed. This cuts carbon emissions by up to approximately 70%, compared with an asphalt or concrete path as stated by the Global Construction Review (GCR) in a “Dutch company to launch prefab plastic roads in 2021” article dated June 01, 2020.
Rajagopalan Vasudevan, a professor of chemistry at the Thiagarajar College of Engineering in India estimated that using recycled plastic in the mix leads to saving of over 3 tons of carbon dioxide per kilometer of road.
According to the International Journal of Innovative Research in Science, Engineering and Technology, when 8% of bitumen is replaced with plastic waste, there is a resultant saving of approximately 350USD per kilometer of road surface.
Further, studies also indicate that as the percentage of plastic waste increases, the compressive and bending strength also increases commensurately leading to longer lasting road surfaces compared to those built by conventional methods. The shredded plastic is added to the asphalt and heated to 170ºC and thereafter heated bitumen is added on top and mixed with the rest of the mixture. All kinds of plastics can be used such as carrier bags and other hard to use plastics.
In India plastic waste is melted and used to fill potholes and make new roads. According to an article in Green Builder Media (2015), plastic road construction was developed in India 15 years ago in response to growing litter. Some of the plastic roads are already four years old and do not show any signs of deterioration (no potholes). There is over 21,000 miles of road made using plastic waste-bit-asphalt mixture in India today.
The government of India decided to make plastic roads the default road type constructed in many major towns in the country.
In the UK town of Cumbria, this technology has been adopted for public roads. Plastic waste is now used to replace bitumen in the asphalt mixture.
In the USA, discarded low grade polymer is mixed with the asphalt. Every kilometer of such roads uses approximately 1 million plastic bags of polymer, saving one ton of asphalt and costing roughly 8% less than traditional roads.
A Dutch company, KWS together with Wavin and TOTAL have developed prefabricated modular plastic roads using 100% plastic waste. These roads are estimated to have a lifespan of two to three times longer than a regular road, are four times lighter and can be constructed 70% faster than a traditional asphalt roadway.
These prefabricated recycled plastic waste roads can have hollow designs so that service cables can be laid through the road deck without need for extensive digging.
In addition, some of the hollow space can be used to store excess water when it rains. Modular plastic roads make repair and maintenance easier as the damaged module can be shredded and recycled back to the same modular road.
A 30 meters bike path in the Netherlands using this prefabricated plastic road design was launched on 11 September 2018 in Zwolle. The company plans to roll this technology out to main roads in the near future.
Recycled plastic waste roads will become the mainstay of road construction in the near future as the case for them is irrefutable. Not only are they generally cheaper to construct, they are more durable and lead to a reduction in carbon dioxide emissions. These are without question, the roads of the future.
Eng. Johnmary Migadde, the Manager KPMG Uganda.
jmigadde@kpmg.com