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

elative rates and patterns of improvement between the two are very similar. This
implies that polymer concentration may not be substantially related to the rate of curing
time improvements in rut-resistance, although the benefits provided through the use of
polymers cannot be fully realized without allotting adequate time for curing regardless of
concentration (see Figure 19). Furthermore, it is important to realize that
microsurfacing curing times are highly dependent upon a number of factors, including
the pH of the asphalt emulsion, the type and amount of surfactant, the type of bitumen
and aggregate, and the application temperature (71).
Setting agents such as Portland cement or lime can be added to microsurfacing mixes
to control curing time by reducing the rate at which water evaporates and the asphalt
emulsion breaks. When used with polymer modifiers, these setting agents aid in
promoting the formation of the continuous polymer networks associated with
quantifiable improvements in the viscoelastic characteristics of thin surface treatments
discussed previously (71). Work by Takamura (2001) proposes substituting aqueousphase
alkali metal hydroxides or salts in place of Portland cement to facilitate
independent control of curing and mixing times based upon aggregate and bitumen type
(71). In addition, mixing accuracy is improved and handling made much easier owing to
the difficulty in metering powdered Portland cement on the paving machine.
100
94
Rutting Resist. Temp. (ºC.)
88
82
76
70
3% Polymer
5% Polymer
64
0 10 20 30 40 50
Curing Time (days)
Figure 22 Microsurfacing Curing Time and Rut-Resistance (54)
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