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

in the literature on the use of polymerized asphalt emulsions on trails and parking lots
as noted previously.
3.2.2 Task 2B. Identifying and Specifying Polymer Percentages
Experience has shown that specifying polymer percentage does not necessarily result
in the expected performance because of differences in compatibilities between asphalt
and polymers from different sources. Moreover, feedback received from industry
participants at the St. Louis meeting in 2006 clearly indicates that suppliers view
polymer quantity specifications as a practice which serves to inhibit innovation – a
problem which can be remedied with the adoption of appropriate performance
specifications.
Thus, performance testing rather than recipe specifications should result in the longest
lasting, most cost-effective treatments, by affording suppliers the opportunity to
prescribe the polymer types, formulation methods, and mix design flexibility to meet
agency and end-user requirements. Specific methods which are currently under
consideration are discussed elsewhere in this report. Because of the importance of
uniformity and compatibility to performance, it is recommended that the polymer not be
post-blended with the asphalt emulsion in the field, particularly since both SHA and
industry stakeholders have openly discouraged this practice.
Low temperature recovery of asphalt emulsion residues will simulate emulsion curing
much more effectively than current recovery methods which are performed at
temperatures that are far higher than these products will ever experience in the field.
The high temperatures associated with currently used recovery methods have been
shown to change the residue rheological properties, as the modulus is usually cut in half
by heating the sample to 350º C, as opposed to using a low temperature Forced Draft
Oven Method. Also, phase angles from high temperature distillation suggest that
heating can cause cross-linking and damage to polymer additives. Therefore, it is
recommended that a low-temperature method be adopted which is more representative
of field curing conditions. Several such methods are under investigation by various
107