Minnesota's experience with scrap shingles in bituminous pavements

The Minnesota Department of Transportation (Mn/DOT) has experimented with the use of shingle scrap in hot mix asphalt (HMA) since 1990. To date, the source of the shingle scrap has been shingle manufacturers exclusively. The manufactured shingle scrap consists primarily of tab punch-outs but also contains some mis-colored and damaged shingles. Test sections were constructed on the Willard Munger Recreational Trail, T.H. 25 in Mayer, Minnesota and on County State Aid Highway (CSAH) 17, in Scott County, Minnesota. Not only are the test sections performing as well as the control sections, but using shingle scrap reduces the amount of virgin asphalt cement required in a bituminous mix, thus creating the potential for cost savings when using shingle scrap in HMA. Based on the performance of these test sections, shingle manufacturing scrap is now an allowable salvage material in hot mix asphalt under Mn/DOT specification 2331.E2e, Recycled Mixture Requirements. This report outlines the history of shingle scrap use in Minnesota, presents laboratory and field performance data and contains the current Mn/DOT specification allowing shingle scrap to be used as a salvage material in HMA pavements.