? The use of roofing shingles in the mix required less compaction effort to densify.
? A mix using 5.0% of factory scrap shingles resulted in a substantial decrease in
cold temperature susceptibility.
? Mixtures containing greater than 5.0% shingles may have a marked decrease in
mixture stiffness without a corresponding positive influence on cold temperature
susceptibility. This may result in an unacceptable stress at high temperatures
and high traffic volumes.
? Moisture sensitivity does not appear to be influenced by the inclusion of shingles
in the mix.
? It appeared that the felt-backed shingle mixes would have an increased ability
to deform in cold temperatures before thermal cracking occurred. Neither
the tear-off or the fiberglass-backed shingle mixes exhibited such behavior.
? Creep compliance analyses led the researchers to conclude that deformation
was reduced when shingles were added to a mix prepared with softer (120/150
penetration) asphalt, but that the opposite was true when shingles were added
to mixtures using the harder (85/100 penetration) asphalt.