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

strain-controlled tests indicate that softer mixes are more fatigue resistant (16).
Moreover, because polymer modified asphalt binders are used as thinly-applied surface
treatments, the physical parameters used to characterize the performance of HMA
mixes (such as the PG specification) may not always be applicable.
The search for physical parameters and related laboratory tests which can be used to
accurately characterize the performance of PME is on-going. The following section
discusses some of the information obtained from the literature review which pertains to
the use and adaptation of various innovative and routine testing protocols that have
been, or which may be utilized for the analysis of PME residue performance.
2.4.2 Testing Protocols and Considerations
Analysis of asphalt emulsion properties may be accomplished by directly collecting a
sample of the non-emulsified binder, or by extracting the properly cured residue from a
prepared emulsion sample. Typical residue extraction techniques include:
• Stirred Can Method – A commonly utilized extraction technique, it involves
constantly stirring a sample of the emulsion for 170 minutes at a temperature of
163º C. to drive-off the water. A blanket of nitrogen gas is used to dampen the
effects of oxidation. Although this method yields abundant quantities of testable
residue in fairly short-order, it has been criticized as not accurately representing
actual field conditions due to the high continuous temperatures which are used
(59).
• RTFO Method – This methodology described by Takamura (2000) is a variation
on the RFTO test used to simulate aging (60). Samples of the emulsion are
rolled in bottles in a temperature-controlled environment at 85º C. for 75 minutes
with a stream of heated nitrogen gas jetted over the emulsion film to facilitate
water evaporation. This method has also received criticism because it can lead
to incomplete water evaporation in certain asphalt emulsions such as CRS-P2,
producing inconsistent follow-up test results (59). However, some suggest that
this method may be useful for quality control purposes at emulsion production
sites since it permits for the rapid extraction of testable quantities of residue (60).
45