Page 69 - MODELING OF ASPHALT CONCRETE

Modeling of Asphalt Binder Rheology and Its Application to Modified Binders 47

Creep Tests at 70°C, 300 Pa Shear Stress
(Loading is Recovery 9s) 100 cycles
14.0

12.0 PG 82-Oxidized

10.0
Accumulated strain 8.0 PG 82-PEs

6.0

4.0
PG-82-SBSr
2.0

0.0
0 200 400 600 800 1000
Time (s)

FIGURE 2-17 Results of the accumulated strain under repeated creep testing for 3 PG 82
binders at selected conditions of 1-second loading and 9 seconds recovery.

Figure 2-17 depicts the results of the repeated creep testing of 3 binders of the PG 82
grade at selected loading conditions of 1 second loading and 9 seconds unloading. The
results show clear distinction between the accumulated permanent strains of the binders
∗
which could not be detected using the G /sind. It can be observed that the elastomeric
binder (SBS) is offering significantly higher recovery during the creep testing and thus
results in less accumulated deformation compared to the other binders.
∗
The results of the creep and recovery and the G and phase angle are listed in
Table 2-4. As shown, the accumulated strain after 100 cycles at 70°C is only 20 percent

SBS
PEs Modified
Modified PG 82-22 Oxidized PG
PG 82-22 (R1B09A) 82-22 (R1B15)
(R1B02)
Total strain at 100 cycles, e 2.389 6.948 11.599
total
∗
G at 300 Pa 10989 11379 15272
d at 300 Pa 56.2 60.3 73.9
sind 0.831 0.869 0.961
∗
G /sind 13224 13100 15895
Ratio of strain at end of loading 2.787 1.656 1.169
cycle (e ) to permanent strain at end
L
of recover (e ) at 1 cycle
p
e /e at 100 cycle 5.571 1.764 1.179
L p
∗
TABLE 2-4 Comparison of the Creep and Recovery Indicators with the Values of G and sind
Measured with the DSR at Small Strains