Temperature and traffic speed effects on asphalt pavement response and the elastic asphalt modulus

This paper provides an evaluation of the relationships for relative effects of temperature, traffic speed and pavement structure on asphalt modulus found in the current Austroads guide for pavement thickness design. To evaluate the relationships, a theory-based viscoelastic model was employed. The effect of rolling wheel loads was studied, using the viscoelastic pavement response to load model which also included asphalt temperature dependency. The responses of the asphalt layer for typical Australian temperatures were computed under speeds between 10 and 100 km/h. From the calculated strains at the bottom of the asphalt layer, an equivalent elastic modulus of the asphalt layer was determined. This modulus used in a linear elastic pavement model will lead to the same critical strain at the bottom of the asphalt layer under a static load. The equivalent elastic asphalt modulus was used to facilitate comparison between the Austroads guide’s relationships and the viscoelastic model behaviour. The relative effect of asphalt temperature and traffic speed from the model was found to be largely consistent with the relationships used in the Austroads guide for pavement thickness design in Australian design conditions.