Comparison of flow number, dynamic modulus, and repeated load tests for evaluation of HMA permanent deformation

• Permanent deformation (PD) is one of the major distresses in HMA pavements.
• Three laboratory tests (FN, DM and RLPD) were comparatively evaluated for characterizing the PD response of HMA.
• The FN Index concept was explored and showed promise in discriminating the PD resistance potential of different HMA mixes.
• Each test method (FN, DM, and RLPD) has its own merits and demerits.

The primary objective of this study was to compare the flow number (FN), dynamic modulus (DM), and uniaxial repeated load permanent deformation (RLPD) laboratory tests, used to characterize the HMA mix rutting resistance potential, and establish if they could be reasonably related to each other, and whether, based on these correlations, one test method can be satisfactorily used in lieu of the others. In addition, the concept of FN Index was introduced to quantify the rutting resistance of HMA mixes. Laboratory test results indicated that the FN Index, in contrast to the classical FN (cycles) parameter, exhibited a better correlation with results of both the DM and RLPD tests.