Hot mix asphalt behaves viscoelastically under temperature changes and vehicle speeds. However, the Austroads design guidelines do not explicitly address the theory of viscoelasticity. The initial flexural modulus of 14 asphalt beams was measured at different combinations of temperatures and loading rates. A parallel framework to Austroads that accounts for the viscoelastic response of typical New Zealand roading mix is presented. This paper found there was a 50 per cent reduction in the flexural stiffness for an increase of temperature by 10 degrees Celsius at 5, 10, and 15 Hertz. An assessment of the Shell fatigue transfer function currently adopted by Austroads design guidelines for fatigue cracking for a typical New Zealand asphalt mix was also carried out. This paper highlights that different empirical fatigue models have different fatigue lives. Hence, there is a need to use appropriate fatigue models, instead of the Shell model, to reflect the fatigue performance of the asphalt and furthermore, address the asphalt material characteristics and loading conditions. (a) For the covering entry of this conference, please see ITRD abstract no. E220164.
Abstract