Page 155 - MODELING OF ASPHALT CONCRETE

Complex Modulus fr om the Indir ect Tension Test 133

FIGURE 5-6 Dynamic modulus mastercurves for (a) I19.0D-Fine, (b) I19.0D-Coarse, (c) B25.0B-Fine,
and (d) B25.0B-Coarse. (Kim et al. 2004, with permission from Transportation Research Board.)

NMAS
9.5 mm 12.5 mm 19.0 mm 25.0 mm All
<0.05 15% 14% 19% 33% 19%
P-Value
>0.05 85% 86% 81% 67% 81%
<5% 48% 46% 28% 25% 39%
5−10% 21% 33% 42% 19% 31%
% Difference
10−20% 21% 21% 26% 19% 22%
>20% 10% 0% 4% 38% 8%

TABLE 5-3 Summary of P-Values and Percent Difference in Dynamic Moduli from IDT and Axial
Compression Tests

First, about 70% of the tests had a percent difference below 10%. Secondly, although
it is not shown in Table 5-3, further investigation of the testing conditions that have high
percent differences reveals that most of the high percent difference come from 35°C data
due to very small dynamic modulus values in the denominator of the percent difference
calculation. Finally, it can be observed in Table 5-3 that the percent difference becomes
greater as the NMAS increases. An investigation of the individual test data reveals the
same trend; that is, the variability among the replicates increases as the NMAS increases.
These observations may be related to the ratio of gauge length to NMAS. Typically, a
factor of 3 is recommended to maintain a representative volume element (RVE). Meeting