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

CHAPTER 4: TESTING PROCEDURES AND RESULTS
During the placement of the modified hot mix pavement sections, MDOT District
Laboratory personnel took samples of the mix and conducted asphalt acceptance tests in
the field laboratory. These results are discussed in this chapter. Also, other tests were
conducted which included the SHRP Gyratory Compactor (SGC), The Corps of Engineers
Gyratory Testing Machine (GTM), the rotational viscometer, tests to determine the “true”
PG grading of the various modifiers, and performance testing of the completed pavement.
ACCEPTANCE TESTS
Results of the laboratory tests on the hot mix samples are contained in Appendix B. The
actual job mix properties have been taken from this information and summarized in table 5.
In addition, the design properties are listed for comparison. The order that the modifiers
are listed in table 5 is the order in which they were paved. A discussion follows for each
modifier and the control section. The air voids mentioned below refer to 75 blow Marshall
specimens.
Air voids determined from the Marshall specimens and from field cores are shown in figure
14 for the HMA binder course and figure 15 for the HMA surface course. For the binder
course, the laboratory air voids are in the range of 3-5 percent with the field air voids
ranging from 4-8 percent. In all cases for the binder course, the air voids from the cores
are higher than those from the laboratory. It is possible that the cores taken from the
pavement received less compaction than did the samples with the Marshall hammer. For
the surface course, the same is true except in one modifier.
KRATON Modifier
All of the actual properties for KRATON were within acceptable limits for the binder but
the air voids were high for the surface. The main property for acceptance is air voids,
which for this mix had a value of 4% for design for both layers with acceptance without a
penalty of +1% or -1%. For the binder layer, the KRATON modifier had air voids of 3.4%
and for the surface layer a value of 5.3%. A second test was conducted to check the air
voids and this sample had air voids of 5.6 %. These high air voids for the surface course
resulted in a deduction to be made on the pay item. Stability for the KRATON modified mix
exceeded the design value for both material layers.
STYRELF Modifier
The air voids for STYRELF were 3.4 for the binder and 5.3 for the surface. A second
sample was tested for air voids and resulted in a value of 5.3 also. A deduction was made
because of the high values. All of the other property values were acceptable. The percent
AC for STYRELF was 4.69 for the binder course, which was slightly on the low side of the
design value of 4.8%. The AC for the surface course was 5.07%, which was slightly lower
than the design value of 5.2%. Both of these values were acceptable. Stability for the
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