Investigation of Rutting Resistance of Superpave 5 Asphalt Mixtures

Abstract

The Superpave mix design method has been used for more than two decades to design asphalt mixtures used in the construction of asphalt pavements. While permanent deformation (rutting) distresses have been virtually eliminated, the durability distresses, e.g., cracking, moisture damage, and raveling, have become the predominant distresses that control the service life of asphalt pavements. A new method, the Superpave 5 design method, was recently developed to reduce this issue and to improve the durability of asphalt pavements. The new method increases the compactibility of asphalt mixtures, which results in increased as-constructed densities of the asphalt mixtures placed in the field. While there is evidence that this new mix design reduces durability issues, there is concern that the increased compactability will negatively affect the rutting resistance of the mixtures. To investigate the validity of this concern, four traditional Superpave 4 (SP4) asphalt mixtures were modified to match the requirements of the new Superpave 5 (SP5) mix design by changing their aggregate gradation to make them more compactable. The compacted specimens were subjected to performance tests, such as SCB (semi-circular bending) test, |E*| (diametral dynamic modulus) test, and flow number test. The performance test results showed that the SP5 mixtures have better rutting and cracking resistance, compared to the original SP4 mixtures, and the concern associated with more compactable mixtures is not valid.