Correlating rutting with dynamic modulus of asphalt concrete

The correlation between dynamic modulus of asphalt concrete and rutting was investigated in the laboratory. Five asphalt concrete mixtures of different stiffnesses produced according to Virginia specifications were tested using dynamic modulus and flow number tests. The dynamic modulus (E*) tests were conducted at a single temperature (38°C) and six loading frequencies (25, 10, 5, 1, 0·5, 0·1 Hz) and flow number (FN) tests, designed to evaluate rutting, were conducted at a temperature of 54°C. An asphalt mixture performance tester was used to perform both the dynamic modulus and flow number tests. The results were used to develop correlations between E* and FN at each of the testing frequencies used. Very good correlation (R 2 = 0·94) was found between E* at 0·1 Hz loading frequency and FN at 54°C. Additionally, the correlation between FN and the slope of the graph of E* plotted against frequency was also found to be equally good (R 2 = 0·95). The results suggest rutting susceptibility could be evaluated using E* testing performed at 38°C. The results of this study may be useful to agencies with field or district laboratories looking for an epigrammatic test to evaluate rutting susceptibility during mix designs and field quality control and quality assurance (QC/QA).