February 27, 2009

Evaluation

Making blacktop green takes planning

IAN HARVEY

correspondent

TORONTO

Roadbuilders need to start thinking green when it comes to bidding on Ministry of Transport Ontario blacktop projects.

The ministry is in the process of developing a points system to evaluate bids, Becca Lane of MTO pavements and foundations told a recent gathering of hot mix producers. The system would be similar to that of the LEED system and others currently used in the U.S. which encourage development of sustainable pavement.

“Sustainable pavement is safe, efficient, economical and environmentally-friendly pavement which meets the needs of present day users without compromising those of future generations,” Lane said. “And it’s a goal of the MTO.”

To attain that goal, she said, the point system aims to promote greater use of innovation, such as more and varied recycled materials, in-place pavement recycling, longer pavement life design, permeable pavement and warm mix over hot mix because it uses much less energy and generates 50 per cent fewer green house gasses (GHGs).

Warm asphalt, which is still in the pilot and trial stage in Canada, is fast gaining traction in the United States as the standard spec among environmentally-conscious municipalities and state road authorities.

Some experts say warm asphalt has several advantages over traditional hot mix because it can be mixed in place and laid at temperatures around 90°C whereas hot mix comes from the plant at 160°C and is usually laid at between 120 to 140°C.

The difference in fumes, energy costs, worker safety, GHGs and even in the cure time before it will accept traffic is well worth the slightly higher cost because of the extra handling and additives it requires.

Higher levels of Recycled Asphalt Products (RAP) are also a must in the future, since they will generate much needed points to qualify a bid as “green.”

With warm mix, RAP levels of 45 per cent are attainable, making it an attractive alternative to hot mix. But hot mix itself is being made with higher levels of recycled content from a wider variety of sources, such as unused household and industrial paints which are collected as toxic waste and then processed to be used as an aggregate coating to block some of the stones’ absorption of asphalt.

Gerry Huber, Heritage Research Group associate director, told those attending a recent seminar on the topic that new public awareness of their responsibility to the environment will impact all sectors of industry.

The ripple effect is being seen in the growth of LEED, which started just over a decade ago in the United States and is expanding into new categories to certify existing buildings, homes and neighbourhoods.

LEED already assigns points for the type of paving used in a project, he said, and additionally there are several other green paving certification programs, all with similar point systems for the amount of recycled materials, the source of those materials and whether they have to be trucked long distances, the method of generating the asphalt mix and the nature of the material itself and whether it is permeable to prevent water run off.

In 2009, Huber said, another standard will be launched, seeking to set national benchmarks. Greenroad is in version 0.9 now he says and assigns 62 points, 51 of which are for the materials themselves.

The energy consumed in paving an average single lane of roadway for one mile in the U.S. is equivalent to the power used by 100 households in a year, he noted, and reducing that consumption will have to be a joint priority for the roadbuilding community.

“Some 90 per cent of used asphalt and concrete now ends up in landfill and that’s a waste,” he said. “Each tonne of asphalt recycled into a mix represents about 200,000 BTUs saved.”

Print | Email | Comment