Technical information

4-17
1E-05
1E-03
1E-01
1E+01
1E+03
1E+05
-20.0 -10.0 0.0 10.0 20.0 30.0 40.0 50.0 60.0
Temperature [
0
C]
Time-Temperature Shift Factor [-]
15.5ºC
a
T
=1.0
-10.0ºC
+4.4ºC
+21.1ºC
+37.8ºC
+54.4ºC
Figure 4.3.2: Combined HMA time-temperature shifting for a reference temperature of
15.5ºC (based on Table 4.3.1).
4.3.2 Falling Weight Deflections
In this subsection an attempt is made to use the layered model, calibrated against APT
data (Subsection 4.2.2) and adjusted using laboratory tests (Subsection 4.3.1), to
forecast peak FWD deflections measured at NCAT (see Table 2.3.9). Given that the
diameter of the FWD plate is 11.8 in. (300 mm) and assuming a load pulse of 0.04
seconds in duration, the ‘speed’ of the loading in the FWD test is 295 in./s (=
11.8/0.04). This is 3.35 times faster than the APT speed (= 295/88). Referring to NCAT
section N1 before it incurred significant damage, the first three deflection tests in Table
2.3.9 are considered. The corresponding HMA temperatures were (respectively): 32.9ºC
(91.2ºF) on November 3, 2003, 16.7ºC (62.1ºF) on December 15, 2003, and 10.1
ºC
(50.2ºF) on January 26,
2004. The appropriate time-temperature shift factors from
Figure 4.3.2 are therefore:
016.0
03.
=
Nov
T
a , 704.0
03.
=
Dec
T
a and 987.3
04.
=
Jan
T
a .
Using these values the adjusted reduced frequencies become:
Hz001.0016.035.30232.0
03.
=⋅⋅=
Nov
r
f .................................................... (4.3.5a)