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

2.9 Impact of Materials Selection
The literature review failed to yield significant available research into the compatibility
and selection of materials used in conjunction with PME based systems. Indeed, thin
surface treatment research in general was found to be lacking overall in this area, with
most investigators concentrating on individual component impacts, or “whole system”
performance (e.g., chip seals).
2.9.1 Polymer Type
A review of the available research indicates no clear empirical evidence that one type of
polymer modifier is inherently superior to another with respect to performance, at least
between the most commonly used types (i.e., SBR and SBS). A recent study of stone
retention in chip seals performed by Kucharek et al (2006) indicates that while latexbased
PME may require more curing time than pre-blended PME to fully achieve the
aggregate retention benefits associated with polymer modification, performance
between the two binder types is comparable after only 24 hours (80). Moreover,
Kucharek concludes that “no special benefit has been observed so far from having the
SBR polymer both inside and around the asphalt binder;” citing the need for additional
research (80).
2.9.2 Surfactants & Emulsion Type
Surfactant chemistry is a complex and multifaceted area of study and as such, is well
beyond the scope of the current review. Although published literature on the variation in
PME thin surface treatment performance with respect to surfactant types is relatively
scant (much of these data are proprietary in nature), a few researchers have attempted
to identify high level differences between modified anionic and cationic emulsions.
Kucharek et al (2006) assessed the chip retention characteristics of a variety of anionic
and cationic emulsions modified with different polymers (80). In this study, emulsion
and whole system (i.e., chip seal) performance evaluations were accomplished using
DSR, the Frosted Marble Cohesion Test, and the Sweep Test for Thin Surface
Treatments. Overall, cationic PME mixes demonstrated considerably higher moduli
during the first few hours of curing than did similarly modified anionic preparations.
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