? The Texas Transportation Institute at Texas A&M University conducted a 1995
laboratory study of incorporating factory scrap and tear-off scrap roofing shingles in
HMA. [9] A dense graded mixture and a coarse matrix high-binder (CMHB) mixture
were selected as the test mixtures. The shingle material consisted of coarse-ground (-
12.5 mm to +4.75 mm) tear-off scrap, fine-ground (-4.75 mm to +180 ? m) tear-off
scrap, and (? 9.5 mm to -180 ? m) fiberglass-backed factory scrap. After preparation
of RS-HMA and control mixtures, the samples were for tested for resilient modulus,
indirect tensile strength, moisture susceptibility, and static creep.
The researchers found mixed results for many of the tests, but noted that the
incorporation of either factory scrap or tear-off roofing has a negative effect on creep
stiffness. The greater the amount of shingle scrap in the mix, the poorer the creep
stiffness results. Primarily based on these test results, the researchers do not
recommend more that 5% shingle waste be used in HMA until further research has
been performed.
The report includes detailed guidelines for shingle processing, RS-HMA mixture
designs, mixture production, and RS-HMA placement and compaction. The report
also includes an example Texas DOT Specification for “Hot Mix Asphalt Concrete
Pavement Containing Reclaimed Roofing Shingles.”
? The Georgia DOT has paved two test sections of road using RS-HMA in 1994 [7].
? The first test involved the 1994 widening and reconstruction of the Chatham
Parkway in Savannah. A 1500 foot length of the northbound lane was repaved
with a 2-inch thick RS-HMA base course, overlain by a 1.5-inch thick RSHMA
wearing course. The fiberglass-backed factory shingle scrap used was
generated by GAF, Inc., in Savannah, and shipped to Baltimore for processing.
Once processed, the shreds were returned and stored under cover at the
asphalt plant. The material was incorporated into the mixture as is convention
recycled asphalt pavement (RAP). No special techniques were used in
placement, nor were any significant problems encountered.