Using Polymer Modified Asphalt Emulsions in Surface Treatments A ...
Using Polymer Modified Asphalt Emulsions in Surface Treatments A ...
Using Polymer Modified Asphalt Emulsions in Surface Treatments A ...
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ag<strong>in</strong>g. For example, if the stra<strong>in</strong> recovery <strong>in</strong> the MSCR test falls off<br />
rapidly with PAV ag<strong>in</strong>g, there would be some concern that the<br />
polymer system is unstable. Such a test method has not been<br />
considered <strong>in</strong> the literature, and this issue rema<strong>in</strong>s a data gap yet<br />
to be def<strong>in</strong>ed.<br />
Aggregate Specifications<br />
It is clear from the survey responses that aggregate requirements must fit the asphalt<br />
emulsion application. For example, chip seal experts typically prefer to specify f<strong>in</strong>es by<br />
assign<strong>in</strong>g a maximum P200%, while microsurfac<strong>in</strong>g designers want a methylene blue<br />
test to control the surface activity of those f<strong>in</strong>es. Although survey respondents generally<br />
favor LA Abrasion over MicroDeval, the few who have actually used the latter th<strong>in</strong>k it is<br />
a much better test, particularly for surface applications where more moisture is present.<br />
It is also generally believed that more aggregate and aggregate/emulsion compatibility<br />
test<strong>in</strong>g will yield better performance. A recent study by Kim has shown how to optimize<br />
aggregate gradation for surface treatments (90).<br />
Although the primary objective of this study relates to the use and specification of<br />
polymer modified emulsions, some effort was also directed towards review<strong>in</strong>g FLH<br />
aggregate specifications for chip seal and slurry/micro applications. Tables 12 through<br />
19 show how current FLH standards compare to other agency specifications<br />
(specifically, TxDOT and CALTRANS), as well as to recommendations com<strong>in</strong>g from<br />
active research projects and unique <strong>in</strong>dustry sources. A quick <strong>in</strong>spection <strong>in</strong>dicates that<br />
FLH aggregate specifications use ASTM/AASHTO standard versions of common test<br />
procedures. Overall aggregate quality requirements are consistent with or exceed those<br />
of most state agencies. Specification of the Adherent Coat<strong>in</strong>g test to control the quantity<br />
of P-200 washed from the aggregate is particularly notable as a less common<br />
procedure that plays a very important role for <strong>in</strong>sur<strong>in</strong>g early aggregate adhesion to the<br />
emulsion residue.<br />
89
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