102
Following fatigue testing, axial and shear frequency sweep testing was conducted.
The analysis of the results indicated that both axial and shear stiffness are sensitive to
mix parameters and test temperatures, including the asphalt content and gradation. The
regression models calibrated for dynamic axial and shear stiffness at 10 Hz are:
where,
| E* | = axial stiffness, and loss stiffness in psi;
| G* | = shear stiffness, and loss stiffness in psi;
AC = asphalt content: - 1 for opt.- 0.5%, + 1 for opt.;
GR = aggregate gradation: - 1 for SP 12.5- mm, + 1 for SP 19- mm;
Va = air void content in percent; and
Temp = test temperature: - 1, 0, + 1 for 15 ° C, 0 is 20 ° C, + 1 is 25 ° C.
The relationship between the dynamic axial and shear stiffness for the mixes
considered in this study was found to be the following:
0.78114
10
*
10
* 37.6
Hz Hz
E = × G
Based on the fatigue test results, the laboratory fatigue life model that could be
used for pavement analysis is the following:
3.44019 * 1.07005
0
1.13 10 2 ( 0.04789 0.26812 )
N = ´ - × e × VFA - × GR × - × E -
f e
10.7313 105 exp( 0.04504 0.05947 0.34265 0.1564 )
10
*
a
Hz
G = ´ × - × AC + × GR - × Temp - × V
17.5153 10 5 exp( 0.03956 0.01256 0.31472 0.11671 )
10
*
a
Hz
E = ´ AC + GR - Temp - V