Building sustainable roads
We are committed to the Queensland Government’s Waste Management and Resource Recovery Strategy, particularly working towards a circular economy.
Using recycled materials has the potential to deliver significant benefits including cost savings, reducing landfill, protecting the environment and our lifestyle, network performance, circular economy and reducing emission.
While research is continuing, we have already identified some ways to reduce waste and emissions to deliver sustainable infrastructure by including glass, tyres, reclaimed asphalt, construction and demolition waste into our roads thereby reducing the amount diverted to landfill.
Glass
Up to to 20% recycled glass can be used in roads.
We are continually investigating innovative methods to utilise recycled crushed glass as a substitute for sand and aggregate in road materials. Up to 10% by mass can be incorporated in asphalt courses, excluding surfacing courses and up to 20% by mass, in unbound granular subbases.
Recycled crushed glass may be used as a partial replacement of the fine aggregate up to 20% of the fine aggregate component in normal-class concrete. This can be applied in footpaths, bike paths, kerbs and medians.
Furthermore, recycled crushed glass can be used as a sand aggregate replacement, as bedding, drainage and backfill sand around pipes and conduits. In some fill applications (example core zone of embankment), up to 100% recycled crushed glass may be used.
Using recycled glass reduces reliance on quarried material and natural sand, reduces the amount of waste sent to landfill and reduces greenhouse gas emissions generated by the production of new materials.
Crumb rubber
We have saved 2.4 million tyres from landfill between July 2015 and June 2025.
End-of-life tyres can be recycled and processed into crumb rubber, which is blended into bitumen to be used in asphalt and sprayed seals.
Crumb rubber not only recycles end of life tyres which diverts waste from going to landfill benefitting the environment but can improve the longevity and performance of roads.
Crumb rubber is typically permitted in bituminous binders in spray seal applications with up to 18% permitted as an alternative to synthetic polymers.
Reclaimed asphalt pavement
Up to 40% reclaimed asphalt can be used in new asphalt.
When pure asphalt is removed from existing roads it can be processed into reclaimed asphalt pavement material which can be incorporated back into new asphalt.
The use of reclaimed asphalt provides cost savings, reduces our reliance on raw aggregate and bitumen, and diverts waste from landfill.
Using reclaimed asphalt can reduce the reliance on non-renewable resources in the mixture. This helps minimise waste sent to landfills and reduce the amount of greenhouse gas emissions associated with the production of new materials.
In situ stabilisation
Up to 8,000 tonnes of raw material could be saved per kilometre of road.
In situ stabilisation of existing deteriorated roads is undertaken by pulverising the pavement layers and mixing various stabilising agents (including cement, lime, fly ash and foam bitumen) with the granulated materials to achieve a strengthened, rejuvenated pavement.
This approach minimises waste sent to landfills while avoiding the need for new pavement materials and reducing the consumption of natural resources during the construction process. It also helps reduce the environmental impacts associated with the quarrying, processing and transportation of new pavement materials.
Various in situ stabilisation techniques are currently employed, including lime stabilisation for subgrades, triple blend stabilisation for subbase layers and cement and foam bitumen stabilisation for unbound granular pavement layers.
Construction and demolition waste
Up to 8,000 tonnes of waste can be diverted from landfill per kilometre of road.
Construction and demolition waste is material recovered from construction and demolition sites such as concrete, brick and glass, and can be used as an alternative to natural aggregates and sand in road bases. Construction and demolition waste can also be used in new concrete, pavement stabilisation, drainage materials and earthworks.
In concrete, up to 20% of coarse aggregate component can comprise of recycled crushed concrete and reclaimed aggregate and up to 20% of the fine aggregate component can comprise of recycled crushed glass.
For unbound pavements dependent of subtype, up to 100% recycled crushed concrete can be utilised, up to 45% recycled crushed brick and up to 20% recycled crushed glass.
We are currently undertaking field trials to utilise construction and demolition waste as backfill in retaining and drainage structures.
We also have completed a stabilised recycled crushed concrete pavement construction trial.
Rubblisation of old concrete pavements
We have completed the first rubblisation trial in Queensland.
Rubblisation is used to transform and recycle existing concrete pavements.
This technique fractures the existing concrete pavement into required sizes and interlocking pieces before a new road is constructed over the top.
Rubblisation not only recycles old concrete pavements which diverts waste from going to landfill benefitting the environment, but also provides a cost benefit.
Crack and seat of old concrete pavements
We have completed our first crack and seat trial in Queensland.
Crack and seat treatment is used to recycle end-of-life concrete pavements to be utilised as a stable foundation for subsequent layers.
The process involves fracturing existing concrete pavement at designed intervals to create required patterns. The ‘cracked’ pieces are then rolled to ‘seat’ them firmly on the underlying pavement layer. A thick asphalt overlay is then applied over the ‘crack’ and ‘seat’ pavement.
This method allows for the reuse of end-of-life concrete pavements to be utilised as an underlying layer in flexible pavements.
Fly ash and ground granulated blast furnace slag
Up to 70% reduction in greenhouse gas emissions from the use of fly ash and ground granulated blast furnace slag (GGBFS) in concrete.
Fly ash and GGBFS are industrial wastes from coal fired power plants and by-product of iron production. These waste products can be used to replace up to 70% of the cement used in concrete.
Up to 35% of the cement used in structural concrete can be replaced with fly ash, up to 60% with a combination of fly ash and GGBFS, and 60 - 70% with GGBFS alone.
Currently, we are working to undertake a field trial to use coal combustion products (CCPs) in crushed rock product blends for pavement construction.
The use of fly ash and GGBFS reduces cost, improves overall performance and durability.
Current research
We are continually researching innovative technologies and using recycled materials to construct sustainable resilient infrastructure which benefits the environment, community and economy.
Plastics in infrastructure
We are continually investing in research to understand the opportunities for incorporating recycled plastics into road infrastructure. The research is considering long-term performance benefits for Queensland’s roads as well as the safety and sustainability of the environment and the community now and in the future.
This research is being undertaken as a collaboration with National Asset Centre of Excellence (NACOE), a joint initiative between TMR, Australian Road Research Board and Western Australian Road Research and Innovation Program.
Recycled materials in earthworks and drainage
We are exploring new opportunities for the use of recycled materials in earthworks, drainage and concrete, focusing on diverting waste from landfill and supporting a circular economy.
Recycled materials such as glass, bottom ash and/or pond ash from coal fired power plants and construction and demolition waste have the potential to be used in these applications.
We are currently running field trials and monitoring the outcomes of using recycled materials in road embankments and drainage infrastructure.
Reclaimed asphalt pavement (RAP)
We are exploring new opportunities to utilise up to 30% RAP in high modulus asphalt (EME2) mix designs in comparison to the existing 15% RAP currently permitted.
Field trials are currently being carried out for use of RAP in embankment and earthwork materials.
Sustainability assessment tool for pavements
We are currently developing a web-based sustainability assessment tool for pavements, to enable a comparison of pavement material types and compositions based on lifecycle sustainability and economic outputs of innovative and base case pavement designs. The tool is expected to be released in 2025.
Use of limestone cement
We have completed trials for the potential use of limestone cement in road pavement and concrete. Use of limestone cement reduces carbon emission compared to use of traditional general-purpose cement.
Resources
- Last updated
- 13 January 2026