A Look into Recycled Asphalt Pavement

A Look into Recycled Asphalt Pavement

Written by Tane Abbott, DPM Consulting Group

DPM Consulting Group were tasked by Stockland Developments to investigate ways to improve the sustainability of a residential subdivision in Melbourne.  Over the past two years, DPM have been incorporating recycled asphalt pavement (RAP) products in Stockland’s land development projects. DPM have been implementing a propriety product manufactured by Downer called Reconophalt which consists of ink toner cartridges, car tyres, plastic bags, and recycled asphalt. This material is an alternative to the traditional wearing course layer of road pavement and is designed to be versatile as it can be manufactured from a range of recycled components. For example, the mix used on a project in Sydney consisted of 25 percent reclaimed asphalt, and saved over 47,000 plastic bags, 1,078 ink toner cartridges, and 71 car tyres from being dumped in landfill.

This innovation cost 12 percent more to implement compared to a traditional wearing course on a local road. The gap reduced to only 3 percent on a higher order collector road. This indicates that Reconophalt becomes more economical when incorporated into larger scale projects. As the technology improves and the industry increases its uptake and appetite for alternative pavement materials this cost will become negligible, if not cheaper, than traditional pavement compositions.

Reconophalt is an example of a recycled asphalt pavement (RAP) product. To address social, financial, and environmental factors which promote sustainability, RAP is a promising innovation. RAP is the collective term for any road product manufactured partially from the reclaimed pavement and waste materials that would otherwise be destined for landfill. RAP can vary in the proportion of recycled materials, which includes reused asphalt, that is mixed with virgin aggregates. The quality of production and calibre of the material ultimately mixed is the deciding factor of how much RAP can be incorporated into the pavement. Depending on the percentage of RAP in the mixture, this product exhibits a higher stiffness which improves structural integrity and increases resistance to rutting, thus reducing maintenance costs over the road’s service life. Pavements constructed from RAP also emit less noise pollution and reduce wear on vehicles.

Road pavement construction consumes a significant amount of energy and emits considerable amounts of greenhouse gases. Roadworks account for around 28 percent of global energy consumption and approximately 22 percent of global CO2 emissions. As existing quarries are depleted it will become more expensive, time-consuming, and laborious to extract the aggregates required to procure the layers necessary for roads. Asphalt has the added drawback of requiring by-products of the oil refining process in the form of bitumen to fabricate the wearing course, which adds to carbon emissions.

Recycling end-of-life pavement and implementing waste materials will lessen the burden on existing landfills, reduce the demand on quarries, and promote sustainability.

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