Estimating Directional Permeability of Hot-Mix Asphalt by Numerical Simulation of Microscale Water Flow

Abstract

Permeability of hot-mix asphalt (HMA) is an important property that influences asphalt's resistance to moisture damage. All current methods used by pavement engineers rely on measuring vertical permeability. Recently, however, it has been shown that horizontal permeability can be much higher than the vertical because of the anisotropic and heterogeneous nature of air void distribution. Laboratory and field measurements of horizontal permeability require sophisticated equipment and detailed procedures that limit the ability to measure this property routinely. This study developed a procedure for estimating the horizontal permeability of asphalt mixes. The procedure requires simple laboratory measurements of vertical permeability and porosity (percent air voids) of sublayers in a specimen. The development of this simple method was supported by numerical simulations of microscale fluid flow in a wide range of HMA mixtures. The simulations helped in understanding the factors that control vertical and horizontal permeabilities. The developed equation and the numerical simulations confirmed that the horizontal permeability is several times higher than the vertical permeability.

Get full access to this article

View all access options for this article.

References

McCann

, Anderson-Sprecher

, Thomas

K. P.

, and Huang

S.-C.

Comparison of Moisture Damage in Hot Mix Asphalt Using Ultrasonic Accelerated Moisture Conditioning and Tensile Strength Test Results. In Proceedings of the 2006 Airfield and Highway Pavement Specialty Conference, American Society of Civil Engineers, Reston, Va., 2006.

Masad

, Al-Omari

, and Chen

H. C.

Computations of Permeability Tensor Coefficients and Anisotropy of Hot Mix Asphalt Based on Microstructure Simulation of Fluid Flow. Computational Materials Science, in press.

Masad

, Al-Omari

, and Lytton

R. L.

Simple Method for Predicting Laboratory and Field Permeability of Hot-Mix Asphalt. In Transportation Research Record: Journal of the Transportation Research Board, No. 1970, Transportation Research Board of the National Academies, Washington, D.C., 2006, pp. 55–63.

Masad

, Muhuthan

, Shashidar

, and Harman

Internal Structure Characterization of HMA Concrete Using Image Analysis. Journal of Computing in Civil Engineering, Vol. 13, No. 2, 1999, pp. 88–95.

Latini

R. G.

Measurement of Directional Permeabilities, MS thesis. Department of Chemical Engineering and Metallurgy, Syracuse University, Syracuse, N.Y., 1967.

Moore

P. J.

Determination of Permeability Anisotropy in a Two-Way Permeameter. Geotechnical Testing Journal, Vol. 2, No. 3, 1979, pp. 167–169.

Hall

K. D.

, and Ng

H. G.

Development of Void Pathway Test for Investigating Void Interconnectivity in Compacted Hot-Mix Asphalt Concrete. In Transportation Research Record: Journal of the Transportation Research Board, No. 1767, TRB, National Research Council, Washington, D.C., 2001, pp. 40–47.

H. G.

Effect of Void Size, Arrangement and Interconnectivity on Permeability of Hot-Mix Asphalt Concrete: Void Pathway Test. MS thesis. University of Arkansas, Fayetteville, 2000.

Al-Omari

, and Masad

Three Dimensional Simulation of Fluid Flow in X-Ray CT Images of Porous Media. Int. Journal of Numerical and Analytical Methods in Geomechanics, Vol. 28, 2004, pp. 1327–1360.

10.

Kutay

M. E.

, Aydilek

A. H.

, Masad

, and Harman

Computational and Experimental Evaluation of Hydraulic Conductivity Anisotropy in Hot-Mix Asphalt. International Journal of Pavement Engineering, Vol. 8, No. 1, 2007, pp. 29–43.

11.

Kutay

M. E.

Modeling Moisture Transport in HMA Pavements. PhD diss. University of Maryland, College Park, 2005.

12.

Kutay

M. E.

, Aydilek

A. H.

, and Masad

Boundary Conditions and Laboratory Validation of Lattice Boltzmann Method for Modeling Pore-Scale Flow in Granular Materials. Computers and Geotechnics, Vol. 33, 2006, pp. 381–395.

13.

McNamara

, and Zanetti

Use of the Boltzmann Equation to Simulate Lattice-Gas Automata. Physical Review Letters, Vol. 61, 1988, pp. 2332–2335.

14.

Maier

, Kroll

, Kutsovsky

, Davis

H. T.

, and Bernard

Simulation of Flow through Bead Packs Using the Lattice Boltzmann Method. AHPCRC Preprint 97-034. University of Minnesota, Minneapolis, 1997.