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

Table 13 illustrates a draft Strawman “report only” testing protocol for recovery and
eventual specification of PME residues. It includes rheological testing using a DSR for
a minimum G*/sin δ and a maximum phase angle to determine polymer properties. The
DSR is further used in the MSCR mode to determine recoverable strain and j nr . High
temperature testing will be done at the T h grade for the base asphalt if known, and two
additional temperatures in 6º C increments above that. It is suggested that new DSR
test methods be developed to predict low temperature physical properties so that the
BBR would not be needed for specification of asphalt emulsion residues. One logical
approach to this problem is to use cone and plate geometry in the DSR to evaluate G*
and phase angle at temperatures ranging from 0-20º C, and then use the CAM model to
predict low temperature properties.
If DSR extrapolation methods cannot achieve sufficient accuracy, then new sample
preparation procedures would be needed to make BBR a viable tool for classifying
asphalt emulsion residues. High-float gel characteristics will be captured through some
yet-to-be-determined method of defining non-linear pseudo-plastic behavior. DSR plots
of ln(G*) versus shear rate or determination of a yield stress should be able to replace
the antiquated float test with more quantitative measures of gel strength. For long-term
residue aging, the PAV is believed to be the best alternative.
Although questions remain as to a specific aging protocol, rheological tests on PAV
residue should characterize low-temperature behavior after aging (brittleness, raveling
potential) and answer the question of what happens to the modified binder as it ages.
Other research teams at WRI and ARC have been approached regarding the possibility
of altering their 2 nd year work plans to develop methods for the DSR low-temperature
specifications, the gel characterization, and PAV aging of asphalt emulsion residues.
Discussions with project principal investigators and FHWA project managers are ongoing.
The expectation would be that the ongoing FLH report-only field study would be
used to evaluate proposed methods and specifications that might come from that
research.
It is expected that samples will be collected and tested from three FLH field projects
during the summer of 2008 as a test run of the report-only concept.
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