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

100
90
100
91
Aggregate Retention (%)
80
70
60
50
40
30
20
49
40
Unmodified
SBR
10
0
1
0
5 C. -10 C. -25 C.
Temperature
Figure 21: Vialit Chip Retention at low Temperatures Chip Seals (4)
Wegman (1991) notes that the improved early chip retention offered by polymer
additives when used in chip seals, allows for greater variation in aggregate and
emulsion application rates, and permits earlier sweeping of the applied surface which
serves to mitigate windshield damage (67).
A survey of chip seal best practices by Gransberg and James (2005) indicates that early
brooming of chip seals immediately after rolling to remove loose stone, is ill-advised
since curing at this stage is generally insufficient to permit proper binder to aggregate
bonding (68). More specifically, although polymer modifiers can significantly enhance
stone retention, research has shown that adequate cure times are needed to realize this
benefit (14, 66) (see Figures 6 and 20). Gransberg observes that chip seals can be
successfully applied to high volume roads, providing allowances are made for adequate
curing time, and that the underlying pavement condition of the roadways selected for
treatment are fundamentally sound (68). Moreover, detailed assessment of chip seal
performance nationwide indicates that the best performing chip seals are those where
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