Computational and experimental evaluation of hydraulic conductivity anisotropy in hot-mix asphalt

Abstract

Moisture damage in asphalt pavements is one of the primary distresses that is associated with the disintegration of the pavement surface, excessive cracking and permanent deformation. Moisture damage is a function of the chemical and physical properties of the mix constituents, and the distribution of the pore structure (microstructure), which affects fluid flow within the pavement. This paper deals with the relationship between the hot-mix asphalt (HMA) microstructure and hydraulic conductivity, which has traditionally been used to characterize the fluid flow in asphalt pavements.

Conventional laboratory or field measurements of hydraulic conductivity only provide information about the flow in one direction and do not consider flow in other directions. Numerical modeling of fluid flow within the pores of asphalt pavements is a viable method to characterize the directional distribution of hydraulic conductivity. A three-dimensional lattice Boltzmann (LB) fluid flow model was developed for the simulation of fluid flow in the HMA pore structure. Three-dimensional real pore structures of the specimens were generated using X-ray computed tomography (CT) technique and used as an input in the LB models. The model hydraulic conductivity predictions for different HMA mixtures were validated using laboratory measurements. Analysis of the hydraulic conductivity tensor showed that the HMA specimens exhibited transverse anisotropy in which the horizontal hydraulic conductivity was higher than the vertical hydraulic conductivity. Analysis of X-ray CT images was used to establish the link between fluid flow characteristics and the heterogeneous and anisotropic distributions within the pore structure.

Keywords:

• Hydraulic conductivity anisotropy
• Asphalt concrete
• Lattice Boltzmann
• X-ray computer tomography
• Image analysis

Acknowledgements

The funding for this project was provided by the US Department of Transportation-Federal Highway Administration (FHWA) through contract No. 03-X00-501. This support is gratefully acknowledged. The opinions expressed in this paper are solely those of the authors and do not necessarily reflect the opinions of the FHWA.

Notes

^|Formerly Graduate Research Assistant, Department of Civil and Environmental Engineering, University of Maryland, 1173 Glenn Martin Hall, College Park, MD 20742, [email protected]

^#Tel: [phone]. Fax: [email protected]

^** [email protected]

Additional information

Notes on contributors

M. Emin Kutay

| |Formerly Graduate Research Assistant, Department of Civil and Environmental Engineering, University of Maryland, 1173 Glenn Martin Hall, College Park, MD 20742, [email protected]

Eyad Masad

# #Tel: [phone]. Fax: [email protected]

Thomas Harman

** ** [email protected]