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 ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
emulsions require a much longer set time than do their hot mix counterparts. In<br />
addition, Serfass et al report that higher SBS contents may be used <strong>in</strong> asphalt<br />
emulsions, s<strong>in</strong>ce modified hot mixes exhibit decreased adhesion and problematically<br />
high viscosities when higher SBS concentrations are used (18).<br />
Gransberg and Zaman (2005) exam<strong>in</strong>ed the relative performance and cost<br />
effectiveness of 342 chip seal projects <strong>in</strong> the State of Texas to compare the efficacy of<br />
hot mix b<strong>in</strong>ders to asphalt emulsions (65). The results of this study <strong>in</strong>dicate that PME<br />
performs at least as well as modified hot mix b<strong>in</strong>ders, and that the former does so at a<br />
lower cost while offer<strong>in</strong>g modest improvements <strong>in</strong> skid resistance and ride quality (65).<br />
The Texas Department of Transportation (TxDOT) generally utilizes asphalt emulsions<br />
<strong>in</strong> their chip seals on lower volume (i.e., < 2,000 ADT) roadways. Moreover, these<br />
asphalt emulsions are typically applied to pavements that are generally <strong>in</strong> poorer<br />
condition as compared to hot mix-based chip seal projects. In such cases, TxDOT<br />
differentiates between asphalt emulsion and hot mix chip seal applications based<br />
primarily on traffic volumes, because the latter requires a shorter cur<strong>in</strong>g time and as<br />
such, reduces lane closure times and traffic delays.<br />
The importance of asphalt emulsion cur<strong>in</strong>g time is further noted by Takamura (n.d.),<br />
who observes that <strong>in</strong> microsurfac<strong>in</strong>g applications, rutt<strong>in</strong>g resistance is shown to steadily<br />
improve when cur<strong>in</strong>g is extended from 1 day to 10 days (2 PG improvement), and from<br />
10 days to 1 month (3 PG additional improvement, 5 PG total). This study suggests an<br />
optimal cur<strong>in</strong>g time of about 20 days for SBR modified asphalt emulsion residue as<br />
shown <strong>in</strong> Figure 19 (54).<br />
2.5 <strong>Surface</strong> Application Types<br />
2.5.1 General<br />
This section presents those f<strong>in</strong>d<strong>in</strong>gs of the literature review specific to common surface<br />
treatment applications where polymer modified asphalt emulsions may be employed.<br />
Among the treatment applications exam<strong>in</strong>ed are chip seals, slurry seals /<br />
microsurfac<strong>in</strong>g, and cape seals. The benefits and limitations of PME are exam<strong>in</strong>ed with<br />
56