American Society of Civil Engineers


Discrete-Element Modeling: Impacts of Aggregate Sphericity, Orientation, and Angularity on Creep Stiffness of Idealized Asphalt Mixtures


by Yu Liu, (Research Assistant, Highway School Chang’an Univ. South Erhuan Middle Section Xi’an, 710064, China; and Dept. of Civil and Environmental Engineering, Michigan Technological Univ., 1400 Townsend Drive, Houghton, MI 49931. E-mail: yul@mtu.edu) and Zhanping You, P.E., (corresponding author), M.ASCE, (Associate Professor of Transportation Engineering, Dept. of Civil and Environmental Engineering, Michigan Technological Univ., 1400 Townsend Drive, Houghton, MI 49931 E-mail: zyou@mtu.edu)

Journal of Engineering Mechanics, Vol. 137, No. 4, April 2011, pp. 294-303, (doi:  http://dx.doi.org/10.1061/(ASCE)EM.1943-7889.0000228)

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Document type: Journal Paper
Abstract: Hot-mix asphalt (HMA) contains a significant amount of mineral aggregate, approximately 95% by weight and 85% by volume. The aggregate sphericity, orientation, and angularity are very important in determining HMA mechanical behaviors. The objective of this study is to investigate the isolated effects of the aggregate sphericity index, fractured faces, and orientation angles on the creep stiffness of HMA mixtures. The discrete-element method was employed to simulate creep compliance tests on idealized HMA mixtures. Two user-defined models were used to build 102 idealized asphalt-mix digital specimens. They were the R-model and the A-model, short for a user-defined rounded aggregate model and a user-defined angular aggregate model, respectively. Of the 102 digital specimens, 84 were prepared with the R-model to investigate the effects of aggregate sphericity and orientation, whereas the remaining 18 were built with the A-model to address the effect of aggregate angularity. A viscoelastic model was used to capture the interactions within the mix specimens. It was observed that (1) as the sphericity increased, the creep stiffness of the HMA mixture increased or decreased, depending on the angles of aggregate orientation; (2) as the angle of aggregate orientation increased, the creep stiffness of the HMA mixture increased, with the rate depending on the sphericity index values; and (3) compared with the sphericity index and orientation angles, the influence of aggregate fractured faces was insignificant.


ASCE Subject Headings:
Discrete elements
Aggregates
Creep
Asphalts
Mixtures
Viscoelasticity
Stiffness

Author Keywords:
Discrete element
Aggregate orientation
Sphericity
Fractured faces
Creep
Asphalt mixtures
Viscoelastic model