Why good specs matter when the rubber hits the road

With ready access to local recycling collections, local governments are leaders in incorporating recycled materials into their roads.

This year, for example, six Adelaide councils – with funding from Tyre Stewardship Australia – are testing the properties of crumb rubber in asphalt.

This initiative will improve understanding of crumb rubber performance under Australian conditions and should encourage other councils to incorporate recycled materials into their roadworks.

But while recycled materials – whether crumb rubber, plastic, crushed concrete, or crushed glass – are becoming more common in local road construction, barriers to their increased use remain.

AUS-SPEC, a joint venture between NATSPEC and the Institute of Public Works Engineering Australasia, has been researching local government trends in the use of recycled materials for roads.

In a nationwide survey of local governments to establish the benefits, difficulties and risks they experience, AUS-SPEC found that reclaimed asphalt pavement and crushed concrete are the most commonly used recycled materials in local roads.

The survey also revealed a growing number of councils are turning to recycled plastic-based products.

This phase of the project culminated in the NATSPEC TECHnote GEN 028 Specifying recycled material for road works using AUS-SPEC and a Project Report, both freely downloadable.

The project’s second phase involved an online survey of Victorian councils in July 2019 inquiring about the types of recycled materials used, the reasons these materials were selected, and the barriers preventing councils from working with such materials more broadly.

The Victorian councils’ top four reasons for using recycled materials in roadworks were: sustainability, cost-saving, better performance than traditional materials, and better availability.

The top four barriers to wider use were: lack of availability, uncertain quality, higher cost, and uncertain performance.

There is wide disparity in local government’s ability to develop recycled road initiatives, with urban councils more likely to be innovative.

In January this year, the City of Greater Geelong announced it would soon resurface three sections of road with a plastic-based asphalt product using shredded plastic from a local recycling plant.

For smaller rural and regional councils, however, projects like Greater Geelong’s – with its high initial costs of collecting and processing recyclables and then developing them into a reliable material for use in public roads – are high-risk.

While some local governments have easier and cheaper access to quarried material than to recycled materials, many more remain uncertain about the benefits of recycled roads, despite being strong supporters of sustainable construction.

Another factor adding to council uncertainty is the relative lack of long-term trials and research on recycled roads in Australia – evident in the paucity of standardised and reliable specifications.

 The six metropolitan Adelaide councils taking part in the crumb rubber trial, for example, are using specifications from California.

The similarities in climate offer a good opportunity to share research and results, but Australian local governments need documentation that is tailored to their own needs. This is the information gap that AUS-SPEC seeks to fill.

AUS-SPEC specifications are based on thorough technical research, are updated every year, and are adapted for local government requirements. As a national system, these specifications for recycled materials in roads will create consistency and minimise the risk factor.

With local councils collectively managing about 80 per cent of the country’s road network, there is immense potential to improve sustainability at the local and national scale.

Quality specifications for recycled materials in roads will assist councils to keep heading in the right direction.

Visit the NATSPEC website for more information.