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

emulsified and non-emulsified asphalt binder tests were similar enough to suggest that
PG test protocols could be adapted to emulsion characterization, although further
investigation is required to establish whether experimental results can be successfully
correlated to field performance (56).
Takamura notes that polymer modified asphalt emulsions can be successfully used in
microsurfacing applications for filling ruts up to 5 cm deep (54). This contradicts the
contention by some that rutting resistance is an inconsequential measurement
parameter when assessing polymer modified asphalt emulsion performance. Indeed,
rutting resistance should prove a valuable indication of a rut-filling mixture’s ability to
resist future high temperature deformation.
Epps et al (2001) have developed a Surface Performance Grading (SPG) system for
asphalt emulsions based upon the modification of existing test protocols used under the
standard PG system for HMA (57). The SPG is designed to take into account the
unique forms of distress common to surface course mixes, such as extreme high and
low temperature performance, susceptibility to aging, stone loss (e.g., from chip seals),
storability, and handling characteristics. Modifications to the standard PG system
generally include adjustments to constant limiting values, as well as some changes to
the actual testing protocols. For example, the PG procedure specifies that the designed
high temperature limit should be determined at a depth of 20 mm below the pavement
surface – a depth limitation which is not applicable to surface treatments. Thus, high
(and low) design temperatures under the SPG are taken to be directly at the pavement
surface.
Determinations of in-place asphalt emulsion performance are dependent upon the
identification of key performance variables, and the measurable physical and chemical
properties of the asphalt binder or emulsion residue which relate to those variables. An
extensive literature review conducted by the Strategic Highway Research Program
(SHRP) has identified five (5) key variables for assessing pavement performance.
These are:
1. Low Temperature Cracking (low temperature susceptibility);
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