Cars can’t drive on roofs…or can they?
The Town of Hassan hopes so. A research project funded by the Minnesota Local OPERA (Operational Research Assistance) Program looks to recycle used asphalt roofing shingles to pave roads.
Hassan Township hopes to cut costs by recycling postconsumer asphalt roofing shingles in pavement.
Mn/DOT currently allows the use of postindustrial asphalt shingles (scrap directly from manufacturers) in paving asphalt. But postconsumer roofing shingles torn off in residential reroofing projects—known as “tear-off shingle scrap”—haven’t been tested as thoroughly. A $10,000 grant from OPERA is helping to change that.
Omann Brothers, the contractor responsible for all project processing and paving operations, has been recycling manufacturers’ asphalt shingles regularly into paving asphalt for more than 15 years, but has not regularly used tear-off shingles. For this project, Omann sourced, sorted, and recycled the tear-off shingles and made sure they were clean enough to meet Mn/DOT and county specifications.
Roofing companies supplied Omann Brothers with about two tons of tear-off asphalt roofing shingles. Omann then paved a 300-foot test stretch of Park Drive just south of the intersection with Tucker Road in the Town of Hassan.
To compare the performance of the pavements, Omann paved a 100-foot test strip with 5 percent tear-off shingles, a second 100-foot strip with 5 percent manufacturers’ shingles, and a final 100-foot test strip without any shingles. The research partners (including Mn/DOT, Hennepin County, the LRRB, and the Town of Hassan) expect the tear-off shingle asphalt to perform just as well as manufacturers’ shingle asphalt in terms of gradation, density, air voids, and asphalt extraction test.
The difference lies in cost. Using recycled asphalt shingles in asphalt reduces the use of virgin asphalt binder, a cost that is rapidly rising, according to a report prepared by the Town of Hassan. The savings to highway departments, the report said, will further encourage research of this technology. Recognizing this value, Hennepin County, Mn/DOT, and Dan Krivit and Associates (the project consultant and coordinator) donated about half the total research cost for labor and consulting.
—Jim Hammerand, LTAP intern