Streets Paved with Reused Waste Material
Using waste materials such as plastics and discarded tyres to reinforce asphalt mixes for highways means less waste goes to landfill and longer-lasting surfaces. In the seventh edition of our construction magazine Building Sight, we look at how the construction industry is tackling environmental issues and aiding countries to reduce emissions and meet ambitious targets.
Worn-out tyres have long been used to reinforce asphalt mixes for roads, particularly in the US, China, and more recently Malaysia. Other waste materials are under trial including plastics, glass, and even toner from used printer cartridges.
As well as diverting waste from landfill, waste materials can improve pavements’ durability and performance, modifying the bitumen in a mix in a similar way to a polymer additive.
India was an early pioneer in waste-plastic roads, with technology to blend waste plastics into hot-mix asphalt at asphalt plants developed at the turn of the century.
Use has ramped up since 2015, when the Indian Government mandated that any urban area with over 500,000 inhabitants must construct roads using the technology.
UK-based MacRebur, whose waste-plastic pellets or flakes have been deployed in roads in Australia, the US, and the UK, claims that a one-kilometer stretch of road made with its binder product contains the equivalent of about 684,000 plastic bottles, or 1.8 million single-use plastic bags.
Melbourne, Australia, has also been home to trials involving the use of plastic bags and packaging, glass bottles, and printer toner in road surfacing.
There are environmental concerns as well as benefits, however.
Heating rubber or plastics to high temperatures can use extra energy and potentially release toxins into the environment.
And plastic roads can potentially degrade, releasing microplastics that attract pollutants such as polychlorinated biphenyls.
Question marks also remain over how successfully roads comprised from these mixtures could be recycled at the end of their useful life.
Thomas Konstantis, a risk engineering consultant in Marsh JLT Specialty’s Construction Practice, says: “It is essential that waste material trial characteristics, such as duration and testing conditions, are clarified prior to actual project application.”
Konstantis says such risks require a comprehensive asset life-cycle management plan, which addresses various challenges, such as health and environmental hazards (for example, toxic byproducts); supply of suitable plastics (including segregation between useable and non-useable plastics); and the project team’s experience and training.