According to the Economist Intelligence Unit's latest Global Liveability Report, the beautiful city of Vancouver in Canada is a pretty decent place to live, ranking third in the world. Its environmental footprint is currently unsustainable, though, prompting officials to hatch an ambitious plan to have Vancouver crowned the greenest city in the world by 2020. Helping things along nicely is a new warm mix paving process that makes use of the kind of waste plastic placed in blue household recycling boxes by conscientious citizens, reducing greenhouse gases and improving air quality along the way.
A team of city officials, including Peter Bremner and Jeff Markovic from Kent Services, has been working with Toronto's GreenMantra to develop an innovative new process that coverts 100 percent post-consumer recycled plastic waste into a wax that can be mixed into warm mix asphalt.
"Warm mix asphalt is not all that new, but what is unique in our application is using a wax that was derived from recycled plastics," Karyn Magnusson from Vancouver's Engineering Services told Gizmag. "We have been trialing warm mix since 2008 with different kinds of additives designed to reduce the viscosity to make placement easier at lower temperatures. We have now paved three sections of Vancouver roads with this latest trial."
"The mix was a 19 mm Superpave, surface coarse warm-mix, with 20 percent reclaimed asphalt pavement and wax derived from blue box plastics," added Markovic. "The temperature was reduced from our typical 320°F [160ºC] to 250°F [121ºC], there's a significant reduction in VOC and CO readings at the plant, and visible reductions in fumes at the both the paver and the plant."
Other benefits revealed in the lab and road trials include 20 percent savings on gas used to heat the mix. Additionally, the City of Vancouver says that there is potential for additional grinding and re-using cycles of pavement, as the wax helps prevent aging of asphaltic oils. Mixing at lower temperatures allows for increased use of recycled asphalt content and lower use of virgin asphaltic oils.
"Paving season is now coming to a close, but next spring we will do some more trials and go back to look at the in-situ performance of the placed material," said Magnusson. "We have some work to do yet evaluating this trial, but if our testing continues to show the benefits we were anticipating then we would love to embrace this as the norm rather than as a special mix. Ideally we will also see somebody begin to produce this wax locally. The material we have used to date was created by a company in Toronto, it would be nice to see Vancouver plastic waste going into Vancouver roads."
Although the new development currently carries a three percent premium over typical hot mix, the developers believe this extra cost will disappear in the near future as a result of an ample supply of waste plastics.
Source: City of Vancouver