Micromechanical Analysis of Viscoelastic Properties of Asphalt Concretes

Abstract

A methodology for relating the microstructure of asphalt concretes to their viscoelastic behavior is described. Imaging techniques are used to capture the asphalt concrete microstructure, and the finite element method (FEM) is used to model its stress-strain behavior in the time domain. Aggregates are modeled as linear elastic, and the binder is modeled through mechanistic models as either linear viscoelastic or nonlinear viscoelastic. The binder viscoelastic properties are input into the FEM algorithm by two methods: a built-in viscoelastic function and a user-specified material characterization subroutine. The latter handles non-linearity in an iterative piecewise linear fashion, whereby the mechanistic binder model parameters are updated as a function of the strain level. For each strain level, mechanistic models are fitted to describe binder viscoelastic behavior based on dynamic shear rheometer data. The two approaches used for specifying binder viscoelastic properties into the FEM algorithm were verified by comparing binder response predictions with direct measurements. Finally, the asphalt concrete micro-structure model was verified by comparing FEM predictions of dynamic shear modulus and phase angle with measurements obtained by using a Superpave® shear tester.

Damage-Induced Modeling of Asphalt Mixtures through Computational Micromechanics and Cohesive Zone Fracture

“…Several studies (Costanzo and Walton 1997;Lagoudas et al 1998) have recognized the importance of including rate dependence in the cohesive-zone fracture law, especially for such inelastic materials as asphalt mixtures. Material viscoelasticity has been reflected in the recent studies by Papagiannakis et al (2002) and Birgisson et al (2002). These studies successfully predict the time-dependent viscoelastic creep behavior of asphalt mixtures.…”

Macroscopic Constitutive Law for Mastic Asphalt Mixtures from Multiscale Modeling

“…Typically, a sufficiently large sample of microstructure of a two-phase composite system, transformed into a binary image, was adopted to serve as a representative volume element (RVE). Either direct application of these models [8,9,10] or application of simplified artificial microstructures of the same type [11] was examined to provide estimates of the macroscopic response. While capturing both the local and overall behavior sufficiently accurately, most of these models suffer from computational inefficiently.…”

Geometrical Evaluation and Experimental Verification to Determine Representative Volume Elements of Heterogeneous Asphalt Mixtures

“…The compacted sample was cut vertically using a diamond saw, and the vertical section was placed on a high-resolution scanner to capture inner structure images. The virgin inner structure image was then processed with sequential image analysis stages as proposed by Papagiannakis et al [20], with the final image capturing only the center portion ͑112 ϫ 112 mm 2 ͒ of the specimen. As shown in Fig.…”