Environmental analysis of using recycled asphalt shingles in pavement applications.

Abstract

Recycled asphalt shingles have been used in paving applications for more than two decades and have growing acceptance in the industry. The cost of asphalt binder has steadily increased, fueling pressure to find suitable recycled materials to supplement virgin materials. The Minnesota Department of Transportation has dedicated several studies for using asphalt shingle scrap in asphalt pavements. There are two types of shingles that can be used in pavement: manufacturer waste shingle scrap and tear off shingle scrap. As a result of the studies performed, the Minnesota Department of Transportation currently allows up to 5% of manufacturer waste shingle scrap in paving applications. Research on tear off shingle scrap is continuously developing, and a draft specification from the Minnesota Department of Transportation indicates that up to 5% can be used in asphalt pavement. In this thesis, both types of shingles were used in asphalt mixtures that were tested for performance to determine if the addition of shingles affects the physical properties. In addition, an environmental analysis was performed. The objective of this research was to determine if it physically makes sense to use shingles in pavement and to understand the environmental implications—which include reducing virgin materials which can yield energy savings. The analysis suggests up to 3% tear off shingle scrap in asphalt mixtures results in an effect on low temperature properties similar to the addition of up to 5% manufacturer waste shingle scrap, if combined with recycled asphalt pavement addition of more than 20%. The results of our research do support previous research efforts regarding the use of recycled asphalt shingles in pavement; however, based on these results, the Minnesota Department of Transportation draft specification for the use of tear off shingle scrap in asphalt pavement should state that up to 3%, not 5%, shingles can be used.