Effects of aggregate size and specimen scale on asphalt mixture cracking using a micromechanical simulation approach

Abstract

A micromechanical model based on discrete element method (DEM) was employed to investigate the effects of aggregate size and specimen scale on the cracking behavior of asphalt mixture. An algorithm for generating three-dimensional aggregates that can reflect the realistic geometry such as shape, size and fracture surface of aggregate particles was developed using a user-defined procedure coded with FISH language in particle flow code in three-dimensions (PFC3D). The parallel-bond model (PBM), linear contact model (LCM), and slip model(SM), whose sets of micro parameters were obtained by comparing experimental tests with numerical simulation results, were used to characterize the internal contact behavior of asphalt mixture. Digital asphalt mixture specimens were used to simulate the effects of aggregate size and specimen scale on the cracking behavior by the indirect tensile (IDT) test. Some conclusions can be drawn as follows: Both cracks and IDT strength decrease with increasing aggregate size. However, the heterogeneity of contact-force distribution augments with increasing aggregate size, especially with 13.2-16 mm aggregate. The aggregate size of 4.75-9.5 mm dominates in forming skeleton structure for asphalt mixture. The IDT strength decreases and cracks augment with increasing sample scale. The crack growth can be well interpreted from the perspective of energy analysis. The conclusions show that the proposed micromechanical model is suitable for the simulation of crack propagation. This study provides an assistant tool to further study the cracking behavior of particle-reinforced composites material such as asphalt mixture and Portland cement concrete.

Keywords

discrete element method / asphalt mixture / cracking / IDT / micromechanics

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