Microstructure modeling of rate-dependent fracture behavior in bituminous paving mixtures

This paper presents a computational microstructure model to predict the fracture-related behavior of heterogeneous and viscoelastic bituminous paving mixtures. In addition to the consideration of the complex geometric characteristics and viscoelastic behavior of the mixture, this study implements a rate-dependent cohesive zone model into the mainframe of ABAQUS in the form of a customized user element (UEL) subroutine. This enables model fracture as a gradual and rate-dependent phenomenon in which the initiation and propagation of discrete cracks take place in the mixture microstructure. In order to validate the model, experimental programs are developed for model inputs and outputs, and microstructural simulations of a two-phase mixture specimen are conducted. Model simulation results agree well with test results. The results presented in this paper imply that a computational microstructure model such as the one herein can be an efficient tool to estimate the effects of small-scale design variables on overall mixture performance with significant savings in experimental costs and time.