Laying Rubber

How might Alberta build better roads and solve a number
of environmental problems at the same time? By giving your tires
a second life in the transportation industry, for one.

Freelance Writer

On the Road Again
Top, elite marathones cross the 012nd Avenue bridge in Edmonton, during the 2001 World Championships in Athletics. Mats made of recycled tires were used to cover the metal bridge deck to protect the soles of the runners' shoes. Bottom, an Edmonton roadway gets a rubber asphalt surface.

Ruts develop in high traffic areas because of the constant pressure of heavy loads speeding up and slowing down. Surfaces dry and contract in the summer to create transverse cracks. And winter is no kinder, with the extreme cold tag-teaming with the freeze-and-thaw cycle of spring to create swells and heaves.

Yes, Albertans and their weather are tough on roads. Engineers and road builders know it, which means they’re always on the lookout for better ways to maintain quality roads at affordable prices.

One idea that shows promise — and a certain amount of poetic flair — is asphalt rubber, now undergoing testing from Lethbridge to Edmonton. In short, your old tires may well be headed back to a road near you.

Roads With Give
Asphalt rubber is formed when rubber “crumb” from recycled tires is mixed into the usual combination of gravel and asphalt oil. The result is a surface that gives under pressure but springs back when the pressure is released.

Tests over the last three years show this reduces rutting. Says Al Schulz, P.Eng., chair of the Alberta Asphalt Rubber Steering Committee: “We haven’t seen the same benefit with cracking yet; our extremes of weather create unique conditions when we compare Alberta to parts of the world where this process has helped with cracks.

“However, there have been enough benefits overall that we have agreed to continue the project for the 2004-2006 paving seasons to provide a good basis for evaluating asphalt rubber.”

Municipal participants also plan to extend their commitment, pending budget approvals. So far Calgary, Edmonton, Lethbridge and Strathcona County have, between them, laid more than 50 kilometres of asphalt rubber — that’s 100,000 discarded tires — and they’re now immersed in monitoring performance and related testing.

First Off the Mark
Calgary was first to apply the new material to an Alberta road when the program began in 2002. “We paved on 112th Avenue Northwest in a rural area that was mainly used by heavy vehicles such as gravel and solid-waste trucks,” says Peter Enslen, P.Eng., the city’s manager of construction and materials for roads. “Although there were the usual glitches you face with any new process, we’ve found it’s performed very well.”

In 2004 Calgary used asphalt rubber for a major stretch of south-bound MacLeod Trail, giving engineers a chance to assess its performance with city traffic. “Asphalt rubber was placed over a surface that had developed fine cracks, which were the result of a hot-in-place recycling treatment from several years earlier,” Mr. Enslen explains. “We anticipate that the rubber mix laid this year will provide a durable surface that will prevent further problems with cracking.”

Lethbridge joined in 2003. “We wanted to contribute to the recycling of tires and we have always been interested in looking at new technologies,” says Al Covey, senior project administrator in Lethbridge. “This process is slightly more expensive than traditional asphalts but it’s worth taking a look at.”

With two years of testing under its belt, Lethbridge has already laid down a healthy section of asphalt rubber, thanks to a climate warmer than most in Alberta and the resulting long paving season. “So far, we’ve used it on a collector roadway and on high traffic areas of the city, connecting it up to roadways with other asphalt surfaces,” says Mr. Covey.

“Next year we’ll try it in a new environment: arterial roadways in residential subdivisions.”
Strathcona County already focuses on urban arterial roads. Bob Horton, P.Eng., county engineer and the manager of engineering and environmental planning, estimates the municipality has laid down 36 km of asphalt rubber over the past three years.

The county is now experimenting with reducing the thickness of the pavement, which Mr. Horton anticipates will bring asphalt rubber costs in line with those of conventional pavements.

“Thickness reduction also results in less aggregate being used,” Mr. Horton says. “We’re hoping that in six years we’ll have the mix right and be able to identify solid benefits.”

Technology Has Improved
Down the road in Edmonton, asphalt rubber is one of several new materials and processes the city is trying. “It’s one more tool in our tool box,” says Hugh Donovan, P.Eng., senior engineer, construction and quality services.

“We experimented with asphalt rubber on our own in 1976 without much success, but the technology has changed, so we were willing to give it another try. This project gives us a chance to look at new material with technological support, shared costs for research and development, and the combined expertise around the table.”

That mix of knowledge is paying dividends for all the participants. The steering committee has representation from Tire Recycling Alberta, Alberta Transportation, the Alberta Roadbuilders and Heavy Construction Association, the University of Alberta, EBA Engineering, Husky Energy and the participating municipalities — the cities of Edmonton, Calgary and Lethbridge, and the County of Strathcona.

“We depend on each other’s expertise,” says Mr. Schulz. “There’s a strong engineering component in the group and representation from senior pavement people directly involved in municipal and provincial paving programs, and from people with pavement industry expertise, who, collectively, are objective and able to piece together the big picture.”

Engineering will provide the hard evidence and cost-benefit analysis needed to prove the product’s long-term efficacy. Besides the data and monitoring conducted by the municipal partners, the University of Alberta provides objective performance monitoring.

EBA Engineering, a firm with paving expertise, has been contracted to provide technical support and analysis. EBA works directly with municipalities to adjust the parameters of the formula to enhance performance.

Quieter Roads
So far, so good. The first three years of data show reduced rutting — and overwhelming evidence of a side benefit enjoyed by residents. Rubber asphalt roads, it turns out, reduce traffic noise.

Whether it’s Groat Road in Edmonton or MacLeod Trail in Calgary, people have taken notice — first of the darker surface and then of the quiet. “We get lots of unsolicited, positive feedback from area residents,” says Mr. Donovan.

Not surprisingly, those benefits have resulted in an extended commitment to the project, including investment in infrastructure. For the first two years of the program, the equipment to produce the asphalt rubber was contracted out of Arizona. However, Fath Industries, an Alberta company, has now contracted for Alberta production, which has made the program more efficient and reliable.

“Alberta is a leader in the field of asphalt rubber,” says Allan Kwan, P.Eng., Executive Director, Technical Standards Branch, Alberta Transportation. “We’re the first province in Canada to experiment on this scale and with this kind of partnership. We plan to keep going until we’ve given it our best try and know whether the product is successful.”

Right now asphalt rubber paving costs more than traditional methods, Mr. Kwan notes, and pavement analysis takes years. “But if, at the end of the road, we find an environmentally responsible product that also has fewer cracks, longer life and less maintenance, the long-term savings will be enormous.”

The Green Factor
Those are environmental as well as monetary savings. Although the tests have used only 100,000 discarded tires to date, the project shows promise to become a major consumer of waste rubber. And other uses are emerging.

Albertans discard three million tires a year, so there’s not shortage of supply. Alberta Environment reacted 12 years ago by deciding to implement an innovative program to transform waste tires from an environmental liability into a useable resource.

Alberta’s tire recycling program has done just that. Since 1993 it has recycled 30 million used tires, absorbing the annual volume of waste as well as tires stockpiled or heaped up in some of Alberta’s old landfills. A surcharge of $4 on each new tire purchase funds the recycling system, which hasn’t needed any other financial support.

The surcharge is collected by Tire Recycling Alberta. As the designated administrative organization that invests and manages the monies in a dedicated fund, TRA provides pay-for-results funding for projects with promise. One of those projects, of course, is asphalt rubber.

Meanwhile Back at the Landfill
But in another bit of poetic justice, tires are also helping Albertans build better landfill sites. In the past, tires were a huge and costly nuisance at landfills — firetraps and mosquito incubators when stockpiled, but tricky space-wasters when buried because of their tendency to “float” through soil.

“Over half the material we recycle is used in civil engineering projects, of which the most common is landfill leachate collection systems,” says Doug Wright, executive director of Tire Recycling Alberta. “A foot of rubber shred is laid at the bottom of a new landfill cell to form a permeable layer to collect leachate and prevent contamination of groundwater. It’s more effective than gravel, which is a scarce and non-renewable resource.”

A Model Worth Copying
TRA has been so successful in these and other endeavors that similar programs are now operating in provinces across Canada.

In fact at home, the group’s mandate was recently expanded beyond tires to other waste recycling. As of Oct. 1, it became an arm of the broader Alberta Recycling Management Authority, which has a new, second division, Electronics Recycling Alberta.

“It is now one organization with two material streams,” says Mr. Wright. “They will be kept as two distinct silos with no cross-subsidization. However, they will be able to share operational efficiencies and the expertise of a shared, experienced board.”

The Road Again
Top, elite marathoners cross the 102nd Avenue bridge in Edmonton, during the 2001 World Championships in Athletics. Mats made of recycled tires were used to cover the metal bridge deck to protect the soles of the runners' shoes. Left, an Edmonton roadway gets a rubber asphalt surface.

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