Mechanical characterization of asphalt tear-off roofing shingles in Hot Mix Asphalt

In the USA, asphalt tear-off roofing shingle is one of the largest productions in the municipal solid waste (MSW) stream. Applications into road construction materials can be an alternative to recycle these tear-off shingles. This paper discusses the beneficial use of tear-off shingles in Hot-Mix Asphalt (HMA) by presenting: (1) the physical properties of tear-off shingles and the extracted binder, (2) the mechanical behaviors and properties of shingle-mixed HMA, (3) an optimum mix design for the shingle used in HMAs. The tear-off shingles obtained from the states of Florida and Minnesota (but main study on the Florida’s shingles) were used for the sample preparation that involves varied amount of shingle addition (ranged from 0% to 6% with 1% increment) for three different virgin binder contents. Laboratory testing methods include a reflux extraction and recovery and penetration tests for the extracted binder and a modified Marshall stability, moisture susceptibility, and asphalt pavement analyzer (APA) tests for the mixtures. The shingle addition causes stiffer binder in the mixture, resulting in the increase of material stiffness, stability, and rutting resistance. A visual inspection of the fractured surface of samples was also conducted to investigate the location of the crack surface either through the aggregates or in the asphalt binder, which is a good indicator of sufficient level of asphalt film in the mixture. Testing results were used to identify the optimum mixing proportion of the tear-off shingle and asphalt binder in HMAs.