Main Roads WA, in partnership with the Waste Authority, and the Department of Water and Environmental Regulation, committed to a pilot project that would use up to 25,000 tonnes of recycled C&D material in various Main Roads WA projects in 2019, as part of Roads to Reuse.
The pilot is being rolled out on two projects:
- Murdoch Drive Connection, which committed to using 4,000 tonnes but has used over 5,000 tonnes; and
- Kwinana Freeway Widening which will use up to 14,000 tonnes.
Under the pilot, material supplied for the trial must meet the Roads to Reuse product specification The specification includes rigorous sampling and testing requirements for C&D recyclers to protect human health and the environment.
Main Roads WA was identified as a key agency to use recycled C&D material, because of the volume of material used each year, and due to the agency’s engineering expertise. Main Roads WA has found recycled C&D to be a high strength and durable material.
A risk analysis was completed prior to the pilot project being undertaken. It identified risks, which were mitigated by Main Roads WA and the Department of Water and Environmental Regulation.
All risks were considered manageable by producing the product under an appropriate management regime (i.e. the RtR framework consisting of the RtR product specification and independent audit) and using the product in suitable applications.
Predicted benefits of using recycled C&D instead of virgin quarry materials included:
- Lower transport costs (due to suppliers of recycled product being located closer to construction sites compared to suppliers of virgin materials)
- Lower emissions from reduced transport
- Reduced disturbance of the natural environment associated with quarrying activities
- Increased use of recycled material, resulting in less material going to landfill.
Other benefits have been observed as a results of the pilot project activities, including:
- Recycled C&D material strength: self-cementing properties can provide benefits for certain applications in road construction. Used as a sub-base, it provides a stiff underlying layer that will help extend the life of various road pavements.
- Additional cost reductions over time: base course under local roads (ideally with geotextile seals) presents initial costs, but these costs are offset by longer life of recycled material
- Time and labour savings: less mixing required because material is more consistent than traditional limestone.
- Water savings: recycled material uses less compaction moisture than virgin material.
- Durability: recycled material functions similarly to conventional granular materials. It is durable and can withstand moderate traffic from construction vehicles without further material breakdown. Conventional materials are more likely to breakdown under the same traffic volume.
Engagement with the Waste and Recycling Industry Association of Western Australia (WRIWA) was important to the development and acceptance of the overall program. WRIWA engaged with industry to ensure that suppliers were aware of the requirements, and ready to supply once the pilot project began. Through the WRIWA , training was provided to the industry on the use of, and adapting practice to the specification.
Main Roads WA has observed the following outcomes from the pilot project, so far:
- The scheme is working
- More product is being used than originally committed to
- The product is good to work with, and is delivering more benefits than expected, including
- Reduced risk of delamination
- Uses less compaction moisture
- Appears to retain moisture (impacts dry-back) – should be trimmed within a day of placement
- 6-13% less water in construction process
- Audit process is working, ensuring good quality product is being supplied, and giving Main Roads confidence in the process
- Recyclers doing the right thing
Main Roads WA has ongoing commitments in the Waste Strategy, and will use increasing amounts of recycled C&D products.
With a heavy forward program of capital works in road infrastructure, Roads to Reuse represents an opportunity going forward for the use of recycled materials.