Inclusion of Moisture Effect in Fatigue Test for Asphalt Pavements

Damage of asphalt mixes due to moisture is a complex phenomenon. Conventional moisture-related tests do not well simulate field conditions, in which traffic loading is an essential component. Flexural beam test has been widely used in current pavement design to evaluate material properties of asphalt mixes, but has not been well explored to study the moisture effect. This paper developed a typical fatigue-based test procedure for comparative evaluation of moisture sensitivity of different mixes. It is a controlled-strain flexural beam fatigue test performed at 20°C, 10 Hz, and 200με on specimens pre-saturated under 635 mm-Hg vacuum for 30 minutes and preconditioned at 60°C for one day. Test results showed that the fatigue based test procedure can distinguish mixes with different moisture sensitivities, and give a ranking of mixes consistent with prior field experience. An extension of the test procedure for use in the pavement design was also discussed, but further work is needed to implement the test procedure.