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

Jones concludes that among the modifiers tested, SBR offers the best laboratory and
long-term field performance in microsurfacing applications (40). While the Schulze-
Breuer-Ruck test appears to be a promising method of assessing the performance of
polymer modifiers, it is noted that resulting measures of adhesion and absorption
provide little or no correlation or distinction between modified and unmodified mixes
(Table 7). Jones also notes that latex modifiers were generally found to outperform
solid polymers in microsurfacings. This likely relates both to the necessitated
differences in mixing methodology (i.e., pre-blending for solids), and the manner and
relative efficiency with which latex may be dispersed relative to bituminous fractions (4,
7, 12, 47, 54). In addition, it has been shown that pre-blending of solid polymers may
necessitate the addition of higher polymer concentrations than in soap batching or comilling
in order to achieve the formation of a continuous polymer network.
2.5.4 Cape Seals
Cape seals represent a combination of a large-aggregate chip seal topped by a slurry
seal coat (or microsurfacing) which is applied approximately 4 to 10 days later. Cape
seals provide a dense, water-resistant surface which exhibits superior ride quality and
skid resistance.
Solaimanian and Kennedy (1998) evaluated the field performance and design
characteristics of 20 cape seal projects in the State of Texas over a period of one year
(72). During this study, bleeding, shoving, and flushing were identified as the most
significant forms of distress in cape seals. Insufficient binder stiffness and failure at the
interface between the chip seal and underlying pavement surface were generally found
to the primary causes of permanent deformation. Moreover, the infiltration and
entrapment of water were indicated to be substantially involved in early cape seal
failure.
It has been demonstrated that resistance to deformation can be increased significantly
through the addition of polymer modifiers to surface-applied asphalt emulsion
treatments (12, 14, 47, 48, 54). This indicates that the use of polymers in the surface
seal or microsurfacing overlays of cape seals can increase pavement life and high
temperature performance. PME slurry seal overlays are also useful to increase chip
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