October 15, 2008

Transportation Association of Canada Conference

University of Waterloo project studies feasibility of recycling asphalt shingles for road construction

DAN O’REILLY

correspondent

Experiments exploring the use of asphalt shingles for highway construction and full-depth asphalt reclamation were recent topics of discussion at a national conference in Toronto.

Those topics emerged during a seminar on recycled materials and processes for sustainable infrastructure at the recent Transportation Association of Canada conference in Toronto.

Who Thought Recycled Asphalt Shingles Needed to be Landfilled: Why not Build a Road? was the title of presentation delivered by University of Waterloo civil and environmental engineering professor Susan Tighe.

A well-known asphalt specialist, she provided some of the results of a research project the university is conducting into the feasibility of using recycled asphalt shingles in road construction.

“Asphalt shingle roofs typically last from 12 to 20 years and each repaired roof produces between eight and 10 tons of waste,” said Tighe, explaining the rationale for the project is to divert used shingles away from landfill sites and incorporate them into asphalt mixes.

Research objectives included determining what percentage of recycled asphalt shingles (RAS) would be optimal in the mixes and how they would work in combination with recycled asphalt pavement (RAP).

In order to measure the performance of mixes with RAS, the university conducted a laboratory study of five different types of mixes with different loading cycles.

Overall, she found the results encouraging.

“Where is this (research) leading us? We think it is possible to have triple solutions — economic, environmental and technical,” she said, adding the study is evolving from the laboratory into fieldwork.

A case study of how using local materials and a reevaluation of the site conditions generated huge material and project savings on a Nova Scotia bridge project was presented by a second speaker.

In the summer of 2007, the provincial transportation department issued a tender for the replacement of a corrugated steel tunnel crossing Highway 10 near the city of Windsor.

The new concrete arch structure was stipulated as “design build” allowing the contractor to use innovative construction techniques, said Paul Proctor, manager of Reinforced Earth Company Ltd., an Antigonish-based consulting engineer.

The contractor reduced the original proposed excavated area after test pit results and other studies proved this was feasible.

As a result, the excavation was reduced by 3,700-square-metres, saving $10,000 and the savings in backfill material was about $100,000, said Proctor.

“The excavated materials around the existing structures were reused for a $20,000 savings and the existing steel arch was sold for recycled scrap metal to a demolition contractor, who hauled it away.”

Another speaker explained that between 2000 to 2004, the Ontario Ministry of Transportation recycled 9.8 million tons of material through full-depth asphalt reclamation.

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