Microstructure Generation of Asphalt Concrete and Lattice Modeling of Its Cracking Behavior under Low Temperature

Abstract

Fatigue cracking has been pointed out as a major distress in asphalt concrete (AC) pavements. It is well known that cracking performance in AC mainly depends on the mechanical properties of its constituent materials, namely asphalt binder and aggregates. Study of such dependence is the key to effective characterization of the mechanical behavior of AC. Previous studies predicted AC behavior from the mixture properties using extensive physical experiments. As an alternative approach to physical experiments, micromechanical modeling, which is composed of microstructure generation and numerical modeling, is introduced in this study.

Digital imaging processing (DIP) of physical specimens to generate microstructures is first investigated, followed by virtual fabrication, which makes use of the mix properties to virtually fabricate the specimen (or the cross section of specimen for 2D analysis), so that the appearance and mechanical behavior of the actual specimen can be simulated.

The resulting microstructure is then processed to obtain a lattice network that is expected to mimic the mechanical behavior of the AC specimen. Lattice modeling approximates a continuum by using a lattice, with each link representing an intact bond that can be broken at any time to create a microcrack. The cracking process is simulated by successive removal of failed links.

Due to the unrealistic computational cost of direct simulation, the multi-scale approach is adopted to perform microstructural analysis, which considers the effect of different-sized aggregates at different length scales. Such an approach reduces the computational cost significantly, while capturing the mechanical phenomena at various length scales.

The effectiveness of the proposed multi-scale modeling approach is then illustrated by modeling the cracking behavior of the uniaxial tension tests under -10°C.

In the end, the effects of surface energy are studied.