Investigation on the mesomechanical performance of asphalt pavements based on mesostructured numerical simulations

Du, Cong; Oeser, Markus (Thesis advisor); Kaliske, Michael (Thesis advisor)

Aachen : RWTH Aachen University (2022)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2022, Kumulative Dissertation

Abstract

Asphalt pavements perform complex linear and nonlinear mechanical responses with respect to traffic loadings. Compared with traditional experimental approaches, the mesostructured numerical simulations can afford a deep insight into the internal mechanism of linear and nonlinear behavior of asphalt mixtures. Based on the two-dimensional (2-D) multiscale simulations, the linear viscoelasticity of asphalt pavements was effectively predicted using the finite element method. Furthermore, the thermodynamic-damage behaviors of asphalt pavements, crack initiations, and propagations were demonstrated by incorporating the cohesive zone model (CZM). However, the computational time and convergence problems caused by the heterogeneous mesostructures cannot be neglected. To improve the efficiency of the simulations, a novel mesostructured model named the "locally homogeneous model" was proposed and successfully applied in two-dimensional (2-D) and three-dimensional (3-D) simulations. The models were divided into several local cells according to the location and size of the aggregates. In each local cell the aggregate and surrounding asphalt matrix were homogenized based on the Mori-Tanaka (MT) method. In terms of the random generation algorithm, the developed locally homogenous model can account for various asphalt mixtures with different aggregate gradations, e.g., dense-graded mixture (AC) and gap-graded mixture (SMA). In the abovementioned model developments, the linear viscoelasticity and elasticity were respectively specified for asphalt mortar and aggregate, and the nonlinear behavior was represented by inserting numerous CZMs. Therefore, the CZMs induced discontinuous crack initiations and propagations, and further caused a large amount of computations efforts and convergence problems. To address this issue, this research proposed a homogenization approach for the nonlinear viscoplastic and damage properties based on the MT method. This approach regards composite materials as homogeneous structures, and represented their nonlinear behaviors by employing the internal state variables. A laboratory creep-recovery test was conducted to determine the linear viscoelasticity and nonlinear viscoplasticity of asphalt mortar. Combined with the locally homogenous model, the nonlinear behavior of asphalt mixtures consisting of different aggregate gradations (AC and SMA) were effectively demonstrated.In summary, comprehensive mesostructured simulations were conducted towards the performance of asphalt pavements at mesoscales. A novel "locally homogenous" model together with the local homogenization approaches were proposed to simulate the linear and nonlinear behavior of asphalt pavements with different aggregate gradations. Several case studies have been presented to prove the capabilities of the proposed models and approaches. In future research, field or in-situ tests should be employed to exhibit the effectiveness of the locally homogenous models in pavement simulations.