Evaluation of viscoelastic Poisson’s ratio of asphalt mixtures

Abstract

The Poisson’s ratio (PR) of asphalt mixtures is an important input parameter in the constitutive models for pavement design and performance analysis. The design and performance analysis of asphalt pavements depend upon measuring proper material properties such as complex modulus and PR. The PR is often assumed to be time independent or it is calculated as the negative ratio of transverse to axial strains in the time domain under uniaxial loading when the time dependency is considered. This study used accurate methods to calculate the viscoelastic Poisson’s Ratio (VPR) under various loading conditions and demonstrated the error associated with using inaccurate methods for calculating the PR. The results demonstrated that the VPR increased with time in uniaxial unconfined tension and compression tests where shear relaxation was generally faster than dilatational relaxation. While the VPR slightly decreased with time in uniaxial confined compression tests where the dilatational relaxation was faster than the shear relaxation. In addition, the results demonstrated that asphalt mixtures with coarse aggregate gradations had lower VPR compared to asphalt mixtures with finer aggregate gradations. Also, the VPR was found to be sensitive to the ageing and moisture conditions. The VPR decreased with ageing and increased with the level and time of moisture conditioning of the asphalt mixtures. Finally, the error introduced by incorrectly calculating the PR as the negative ratio of transverse to axial strains in the time domain was found to be significant in some cases, while it was insignificant in others.

Keywords:

• Asphalt mixtures
• Poisson’s ratio
• viscoelastic Poisson’s ratio
• ageing
• moisture damage

Acknowledgement

Part of the experimental measurements used in this study was conducted in the Asphalt Research Consortium project at Texas A&M University, which was funded by the Federal Highway Administration.