Do we know enough about recycled plastics yet to be laying them on our roads?

A technical report on the benefits and challenges of using recycled plastics has been published in the wake of overseas countries banning the import of Australian waste and the growing interest in using recycled resources in local infrastructure.  

Viability of Using Recycled Plastics in Asphalt and Sprayed Sealing Applications found that waste plastic can act as a partial aggregate replacement in bituminous mixes and a binder extender without having any significant influence on the properties of the asphalt mix. However, not all recycled plastics are suitable for bitumen modification at high temperatures.

It also reports that while there may be environmental benefits associated with the use of recycled plastic, there are concerns about potential health and safety hazards for road workers while handling these materials, their sustainability impacts, and effects on the surrounding environment.

“We conducted a comprehensive local and overseas literature review and found that some waste plastics can be a partial aggregate replacement in bituminous mixes and a binder extender without significantly influencing asphalt properties,” said Christina Chin, Principal Consultant and State Manager (Victoria), Level 5 Design, and principal author of the report.

The review found that most laboratory trials conducted overseas were not performed in accordance with Australian bitumen standards and specifications. Very little is known about the manufacturing processes of the commercially available proprietary products currently being trialled on Australian and New Zealand roads.

“As a result, there are concerns about hazards road workers could be exposed to while handling recycled plastics,” said Chin.

“Some plastics, when heated, release toxic emissions such as chloride, formaldehyde, toluene and ethylbenzene. Another major concern is microplastics leaching out from our pavements into waterways, posing a serious threat to marine life. We don’t want to solve a waste disposal problem by creating another.

“We therefore strongly recommend a precautionary approach until more research has been conducted. A governance framework should be adopted for using recycled plastics on Australian and New Zealand roads containing information about the pavement’s long-term durability; comprehensive health, safety and environmental risk assessments; and storage stability based on Austroads specifications and local working conditions.”

Chin also recommends an independent review of the most commonly used proprietary products containing recycled plastics, to give road authorities a better understanding of their properties.

“It is worth calculating the lifecycle impacts of recycled plastic-modified asphalt and comparing these with impacts of conventional asphalt to quantify their sustainability benefits,” she said.

“These can be established by using the Infrastructure Sustainability Materials Calculator developed by the Infrastructure Sustainability Council of Australia.”

Other recommendations in the report include:

• developing performance-based specifications to allow producers more flexibility to innovate - in return, they are required to provide performance guarantees regarding their products;
• nationally monitoring, assessing and sharing results of road trials conducted in Australia and New Zealand;
• more research into the viability of using recycled plastics in sprayed seals.

Download the free report here.