Algorithms for Generating Air-Void Structures of Idealized Asphalt Mixture Based on Three-Dimensional Discrete-Element Method

The air-void structure of an asphalt mixture is a very important feature because it significantly impacts the strength and modulus of the material. Consequently, in-depth research into an air-void structure for quantification using computer processing is of significant interest. This paper describes the development of a discrete-element method used to build an air-void structure of an asphalt mixture by identifying its inner characteristics, such as its content, size, shape, and distribution. Based on structural construction software called the Three-Dimensional Particle Flow Code (PFC3D), several user-defined algorithms were developed to generate these characteristics in idealized asphalt mixture specimens. Thereafter, algorithms were developed to simulate a triaxial compression test to investigate the stress-strain response of the asphalt mixture. It was proved that the discrete-element models and algorithms developed in this study can suitably depict the characteristics of air-void structures within an asphalt mixture. In addition, the results of a virtual simulation test indicate that the increase in air voids within an asphalt mixture can change the modulus of the mixture by altering the distribution of the internal force chain and the stress-strain response. Furthermore, the impacts of the characteristics of an air-void structure on the modulus prediction of an asphalt mixture were also determined in this study. (c) 2018 American Society of Civil Engineers.