Page 216 - MODELING OF ASPHALT CONCRETE

194 Cha pte r Se v e n

For the VP modeling, repetitive creep and recovery tests with fixed time and fixed
stress are performed. The permanent strains at the end of rest periods are used to
determine the p, q, and Y values. The p, q, and Y values in compression are found to be
20
2.088, 2.482, and 6.33 × 10 , respectively.

Verification of the VEPCD Model in Compression
The VEPCD model in Eq. (7-43), with the creep compliance converted from the complex
modulus, the damage characteristic relationship (i.e., C versus S curve), and the
determined p, q, and Y values, are used to predict the stress-strain behavior of the asphalt
concrete subjected to repetitive creep and recovery loading. It is noted that the loading
portions of the creep and recovery tests provide the data that were not used in the VP
model characterization.
Figure 7-21 shows the viscoelastic strains for the entire loading history and the
viscoplastic strains at the end of the recovery period predicted from the VEPCD model.

FIGURE 7-21 Measured and predicted strains from the fi xed stress creep and recovery tests:
(a) 25°C and (b) 40°C.