Using Polymer Modified Asphalt Emulsions in Surface Treatments A ...

damaged by temperature. The problem is that oxidation reaction rates
double for each 10°C increase in temperature. Therefore the rate of
oxidation in the PAV should be approximately 16 times slower at 60°C
than at the 100°C (212°F) condition used for most Superpave binders. To
reach an equivalent level of oxidation, the PAV testing time would have to
be increased from 20 hours to 320 hours if temperature were reduced to
60°C. Extensive time-temperature PAV aging studies were conducted at
WRI during SHRP. Such data would be valuable in evaluating alternatives
for asphalt emulsion residues. Further research will be needed to
determine the maximum temperature to which residues can be heated
without damaging latex-induced polymer networks.
o
Performance tests to be run on PAV-aged residues should include:
• Low Temperature Performance Specification: As asphalt ages, it
becomes more brittle and prone to cracking at low pavement
temperatures. Hence, low temperature physical properties should
ideally be measured on appropriately aged residues. For surface
applications such as slurry/micro or chip seals, the level of asphalt
oxidation should be comparable to that observed near the surface
of HMA. Physical tests on the aged residue should report both a
hardness parameter and a relaxation parameter. For example, low
temperature specifications could be based upon Stiffness (S) and
“m-value” as measured by the Bending Beam Rheometer (BBR), or
dynamic modulus (G*) and phase angle as measured by a DSR.
• PAV Aging to Control Polymer Compatibility/Degradation: Because
standard test methods which control polymer/asphalt compatibility
have been removed, there is some risk that unstable
polymer/asphalt blends might prematurely degrade or separate.
One possible means to control this could be to evaluate the
polymers contribution to physical properties both before and after
88