There seems to some new and interesting surges of interest in using recycled material in roadways, both for economic reasons and to find a second life for materials destined for the trash heap.
For example, Eileen recently wrote about new work conducted at Michigan State University showing the benefits of using ground waste glass in concrete (which, besides potentially diverting glass from landfills, also reportedly made the concrete stronger, more durable and more resistant to water). This glass-concrete mix was field tested at several sites on the MSU campus, including driveways, heated pavements, sidewalks, gutters, curbs and parking stands.
In fact, the concept of using recycled materials for roadways and the like has probably been around as long as old asphalt has been dug up and concrete has been demolished.
My (limited) memory of efforts to both innovate and standardize some of this work goes back to the mid-1970s when Delbert Day (before his Mo-Sci fame) and Robert Schaffer did their pioneer work on demonstrating how to best mix surplus waste glass with asphalt, which they named “Glassphalt”, and which eventually led to their publishing the Glassphalt Paving Handbook.
But there are apparently enough new projects of this type sprouting up (and promoters proclaiming the “green” benefits that can be accrued) that a group rooted in the University of Washington felt the need to set up a nonprofit organization to establish a rating system for transportation infrastructure projects. Named the Greenroads Foundation — this new group seems to be similar to the now-ubiquitous Leadership in Energy and Environmental Design (aka LEEDs) certification developed by the U.S. Green Building Council.
Greenroads actually was formed in 2010 by the University of Washington’s Department of Civil and Environmental Engineering and CH2M Hill an international engineering design firm. And, after one formative year under its belt, Greenroads has issued its first certification: It has awarded a “silver” certification to Bellingham, Wash., for that city’s use of what it calls “Poticrete,” i.e., concrete, in which the aggregate is made from crushed used porcelain toilet components.
A news release from the University of Washington provides some of the history behind the Poticrete project. Bellingham had plans for a multi-use recreation trail project known as the Meador Kansas Ellis Trail, the final link of the much larger Whatcom Creek recreation trail. Because the planned route for the trail passed through an urban area of the city, responsibility for constructing the various walkways, bike paths and bridges fell to the city’s Department of Public Works.
When city project engineer Freeman Anthony heard that a local nonprofit organization was replacing old toilets for more efficient new ones and was getting ready to pitch out 400 old commodes, he had the idea that maybe they could be put to better use than being dumped in a landfill. Anthony contacted a ready-mix concrete company, Cowden Sand and Gravel, to see if they could be recycled into aggregate.
In the news release, Anthony recalls his conversation with the managers at Cowden. “They said: ‘Yeah, I think we can do something with that,’ We’ll throw it through the crusher and see what we come up with’, ” says Anthony. In the end, the crusher rendered about five tons of toilets into aggregate that was used to make the Poticrete. The porcelain chunks amounted to about one-fifth of the volume of the concrete in the 250-square-yard section in which it was used.
There wasn’t enough Poticrete to complete the entire project, so Anthony used another 80 tons of recycled concrete in the remainder of the trail’s sidewalks, curbs and gutters. In part of the roadway that required asphalt, 30 percent of it was made up of recycled content.
The Poticrete project isn’t the first “green feather” in the Whatcom Trail’s hat. It has already been recognized for using low-energy LED streetlights and employing porous concrete to manage storm water.
The Poticrete effort wasn’t a recycling-for-the-sake of recycling projects, though. Public Works officials say that the cost of crushing the toilets costs “was about the same as using virgin aggregate from regional gravel pits.”
According to the Greenroad’s website the Bellingham certification represents the first fruit of many years of behind-the-scenes work. “Sustainable roadways are not just a dream. This certification means that Greenroads’ five years of research and development has finally become a reality,” says Jeralee Anderson, executive director of Greenroads Foundation. “The Meador Kansas Ellis Trail project is a great example of the mission of the organization and further defines the practical steps that can be taken to green our roads — both nationally and internationally.”
Greenroads says its rating system parallels international standards and covers the best practices of sustainable roadway design and construction in the areas of water, environment, access, community impact, construction practices and materials. Projects nominated for certification must prove they deserve points for having achieved 11 minimum “Project Requirements.” In addition, a project can earn up to 37 extra “Voluntary Credits.” Greenroads, then, according to the website “assigns a project score based on the number of points earned by meeting the requirements and achieving credits. This score translates to one of four certification levels: Certified, Silver, Gold and Evergreen.”