? Ross & Associates evaluated the potential use of RS-HMA in North Carolina. [2] The
research included laboratory testing of three HMA mixes each utilizing three increments
of shingles content (0.0%, 5.0%, and 10.0%). An SMA containing 8.5% shingles and
a control SMA containing 0.3% added fiber content were also tested. The results of
the testing indicated that:
? Tensile strength decreased as the concentration of shingles increased.
? The addition of 5% or 10% shingles to the mix significantly hardened the
asphalt binder, in some cases more than two penetration grades harder.
? The RS-HMA mixes showed decreased susceptibility to rutting based on
dynamic creep tests and loaded wheel testing. The authors attribute this benefit
to the increased stiffness of the asphalt binder, and the hard, angular granules of
the shingle aggregate.
? The performance of the shingle-containing SMA was equivalent to the control
SMA.