State Study 111 - Polymer Modified Hot Mix Asphalt Field Trial.pdf

as would be expected for new pavement, that the measurements for rut depth were
insignificant. The International Roughness Index (IRI) for all sections were all less than 1.6
mm/m indicating excellent ride quality.
Skid tests were conducted for all nine sections. These values were obtained for the total
sections as given in table 7. The average skid values range from 47 to 51. All of the skid
numbers were above 35 indicating acceptable surface friction for all sections.
FWD tests were conducted on each section but the test section was limited to 500 ft within
the overall section. Readings were taken every 25 ft through out the section. The
deflections obtained are shown in figures 21 through 29. For the KRATON, STYRELF,
and NOVOPHALT modifiers, the deflection values were below 0.003 in. The other
modifiers had deflections that were less than 0.005 in. All of the sections have adequate
structural capacity for the design traffic year.
Rut measurements were manually obtained subsequent to construction in both the inside
and outside wheel paths of the outside lane of each test section. Both the measurements
and the months these measurements were recorded are graphically depicted in figures 30
and 31. Appendix C lists the rut measurements that were averaged for use in these
figures. The control section consistently experienced the greatest amount of rutting. Table
8 provides a ranking of the different modifiers based on manual rut measurements.
The Automated Pavement Analyzer (APA) was used to test cores and pills of the various
modifiers. All of the APA test results presented in this report are from testing samples in
the dry condition. Figure 32 shows average rut depths at 8,000 cycles and 120 0 F for both
cores and pills. For the pills the Control mix experienced the greatest amount of rutting
and the Styrelf modifier experienced the least amount of rutting. For the cores the rutting
observed in both the Cryopolymer Rubber and Ultrapave modifiers exceeded the Control
mix and the Seal-O-Flex modifier experienced the least amount of rutting. Table 8
provides a ranking of the different modifiers based on APA results of the pills from this
figure. The pill rather than the core was selected for the basis of ranking in Table 8 since
more uniformly prepared samples are used for comparison testing.
Figure 33 shows APA average rut depths of cores at 8000 cycles and at both 120 0 F and
147 0 F. At 147 0 F the Control mix experienced the greatest amount of rutting and the Styrelf
modifier experienced the least amount of rutting. At 120 0 F the rutting experienced by the
Cryopolymer Rubber and Novophalt modifiers exceeded the Control mix and the Styrelf
modifier experienced the least amount of rutting. Table 8 provides a ranking of the
different modifiers based on APA results of the cores at 147 0 F. This temperature was
selected instead of 120 0 F for the comparison in Table 8 since this temperature better
corresponds to the temperatures experienced by asphalt pavements on hot summer days
in Mississippi and with the PG grade for Mississippi. Note that no Multigrade modifier
cores were tested at 147 0 F.
The rut rankings in table 8 are the manual rut measurements, APA rut measurements on
cores at 147 0 F and APA rut measurements on pills at 120 0 F. Five of the eight modifiers are
within two rankings relative to each other; i.e., for example, the Styrelf modifier is ranked
either first or second among the three rut rankings, Seal-O-Flex is ranked either second or
third and so forth. The Kraton modifier is within three rankings and a greater dispersion is
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