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

and contamination were substantially greater than were found during asphalt emulsion
residue trials. It is hypothesized that this performance differential between modified
asphalt binders may be due to the evaporation of water from the former, which provides
a better barrier to oxidation, and hence aging (52). Therefore, it is suggested that
modified asphalt emulsion storage and handling protocols should focus primarily on
preventing excessive water loss and phase separation rather than on aging-related
problems (53).
2.4 Performance
2.4.1 Performance Criteria
The performance enhancing characteristics of polymer additives are generally twofold -
offering increased resistance to permanent forms of deformation such as rutting and
shoving (high temperature susceptibility); and providing improved durability with respect
to the formation of load-associated types of pavement distress (i.e., fatigue cracking).
Polymers can also afford additional benefits by reducing the formation of non-load
associated cracks caused by roadway brittleness which often occurs in pavements that
become excessively stiff and hard at low temperatures. In this regard, properly modified
asphalts demonstrate improved temperature susceptibility characteristics by remaining
flexible at low temperatures, while retaining sufficient stiffness at high temperatures to
resist permanent deformation.
Some initiatives have been undertaken to develop a “Superpave-like” specification for
surface applied asphalt emulsions. At present, ASTM D977-05 Standard Specification
for Emulsified Asphalt utilizes some aspects of Superpave in its testing and
characterization protocols. Hazlett (1996) asserts that many of the Superpave
performance criteria, such as rutting resistance, thermal cracking, and RTFO aging, are
not applicable to surface applied treatments (55). Moreover, while some forms of
Superpave testing could be extrapolated to polymer-modified emulsified asphalts,
certain specification limits may not be appropriate for pavement surface conditions.
However, Clyne et al (2003) utilized Superpave specifications to test polymer
modified asphalt emulsion residue for cold in-place recycling applications, in a manner
similar to that of asphalt binder (56). Comparisons of resulting data trends from
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