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Greening Asphalt

July 21, 2015

as·phalt

ˈasfôlt/

noun: asphalt

 1. a mixture of dark bituminous pitch with sand or gravel, used for surfacing roads, flooring, roofing, etc.

    synonyms:  tar, pitch, paving, blacktop, tarmac

    "a fresh layer of asphalt"

Otherwise known as a sticky, black and highly viscous liquid or semi-solid form of petroleum, which just so happens to be essential for the auto driving masses.

PelletPATCH at work in AmherstAt NERC’s Fall 2014 Conference, attendees learned about waste tires being repurposed for rubberized pavement and pothole repairs. A demonstration of the rubberized pavement in action was also provided when potholes were filled by PelletPATCH in front of the conference location (much to the delight of the Amherst, Massachusetts Public Works Department).

With roughly 300 million tires discarded in the US every year, recycling them into pavement seems like a great thing. According to Allan M. Olbur with PelletPATCH, asphalt rubber has “proven long term performance, cost effectiveness, and sustainable market growth.” Mr. Olbur states that life cycle costs analyzed by Oregon State University in Arizona, California and Texas where asphalt rubber is widely used, showed significant savings over the life of the project, as much a $7.34 for every square yard of pavement. And, best of all asphalt rubber use helps reduce our use of petroleum and serves to lower our carbon footprint.

Getting more rubberized pavement to be used, however has its challenges, including the need for municipalities and State DOTs to approve specifications,  modifying bid processes to include rubberized asphalt, and, of course adoption by paving contractors.

Advocates of rubberized asphalt are hoping that the use of rubber in asphalt pavements will increase once the Federal Highway Administration (FHWA) updates its 1992 State of the Practice: Design and Construction of Asphalt Paving Materials with Crumb Rubber Modifier. The industry has seen a great deal of innovations and improvements, along with proven results, since these standards were published more than two decades ago.

A recent article in the Boston Globe—Green asphalt? A plant-based compound may undo aging, boost recycling states that the Warner Babcock Institute for Green Chemistry in Wilmington has developed a new plant-based compound, Delta-S, which “rejuvenates” old asphalt so that it will mix better with new paving material. This will allow pavers to utilize a higher percentage of old asphalt when paving, thus reducing costs and petroleum use.

Some asphalt is already recycled into new pavement, but of course more pavement recycling would be another good thing. Currently only about 25 percent of new pavement can contain recycled material. According to the Globe, Delta-S can increase the recycled asphalt content of new pavement up to 50 percent.

Also notes the article, oxidization is the primary culprit that wears out asphalt. Petroleum compounds combine with air, resulting in dry, brittle pavement, leading to cracking and crumbling. (An interesting factoid indeed! And, we Northeasterners blame it all on the snow and ice…) Delta-S reportedly softens pavement and reverses the oxidization that has occurred.

Delta-S is currently being tested in a few locations. So, while the jury is nonetheless out, the innovation is hopeful.

With about 2.65 million miles of paved roads in this country (according to the Federal Highway Administration), reducing the amount of asphalt used would be highly beneficial. About 75% of current paving is with conventional asphalt, increasing rubberized asphalt use and using Delta-S, if it’s proven effective, will help to reduce paving costs and benefit the environment.

In a time when states and municipalities are struggling to keep up with financing road pavement infrastructure needs and congress wallows away its time fighting over if and how to continue funding for the federal contribution to this infrastructure, these two opportunities deserve our vocal support as material managers!

PelletPATCH proudly demonstrated by Sal Marra

By Athena Lee Bradley

Comments (2)

  1. Athena Lee Bradley:
    Jul 22, 2015 at 09:31 AM

    Not sure of Delta-S cost, but as it can lead to use of a higher content of recycled asphalt it should lower overall costs. Both can be used on any asphalt surface and for pothole repair. My understanding is that both recycled tires and Delta-S are mixed with old asphalt to layout as new asphalt.

  2. Carol:
    Jul 21, 2015 at 03:46 PM

    Cost? Future for our driveway repair? Can it go over old asphalt?

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