Roads and pavement materials consist mostly of crushed rock and aggregate there is opportunity to utilise alternative more sustainable materials incorporating recycled products. VicRoads sent out a technical note that intended to provide guidance in the use of recycled materials in pavement and road works as an alternative to the use of conventional material which is produced from quarried sources.
The reason the Victorian Government has started this initiative is because accessible sources are becoming limited even though the geology in Victoria provides high quality rock. The expansion in residential land and associated environmental constraints have hindered the extensions or construction of rock quarries which would now be very costly and time consuming to build. Therefore, metropolitan or urban sources of quarried product is finite.Transporting material across over long distances increases the carbon footprint of road construction and road wear.
In Victoria, there are steady supplies of recycled materials such as crushed concrete, newer basalt surface spalls (NBSS), reclaimed asphalt pavement (RAP) and crushed brick. Using recycled materials contributes towards making non renewable rock resources last longer.
What is the sustainability of using recyclable materials?
Less than 10% of the plastic that has been produced since the 1950s has been recycled. Most of it ends up being dumped in a landfill. Some of the plastic is left to litter the natural environment, where it often ends up in rivers and getting washed out in the sea. ‘380m tonnes of the stuff are likely to be made this year’ the article in the Economist quotes.
That is more than three times as much as the 120m tonnes of bitumen produced annually, most of which goes into building the world’s roads.
Plastic is derived from petrochemicals, while bitumen is produced as a by-product of refining oil. Both of them are polymers which consists of long strands of molecules bound together firmly. This characteristic of plastic makes it stronger and last longer. These features are particularly useful for road builders, who could use hot bitumen to put together aggregates made from broken rocks and stones into asphalt. So why not swap one polymer for another?
The use of crushed concrete by VicRoads
Crushed granular materials as shown in the above photos must be registered with VicRoads Code of practice RC500.05. The registration of such material is a must before it can be used to build any of the roads.
Asphalt mixes must be registered under the Code of Practice RC500.01 Registration of Bituminous Mix Designs pior to use on any VicRoads works.
All mix designs registered with VicRoads are issued its status according to the level of compliance with the VicRoads code of practice.
VicRoads Standard Section 407 Hot Mix Asphalt permits processed RAP (see figure 5) to most dense grade asphalt mixes. The maximum RAP to be added depends on the mix type, the loading and service conditions.
Milled or excavated asphalt known as RAP obtained from the road and other sources can be collected as a co-mingled stockpile (see figure 4).
Glass fines which are manufactured from container glass cullet by crushing and grading to a 5 mm cubical product it is able to meet the requirements for some filter materials in Vicroads Standard Section 702 Subsurface Drainage.
Learn from the Manager of Asset Management at VicRoads, David Jansen, on the functionality of using recyclable materials for road construction and how to design an asset management plan that promotes the safety of the road.
David will be presenting at the 8th Annual Road Engineering & Maintenance Conference on the 14th & 15th May 2019 in Sydney.