Quantification of movements of flat and elongated particles in hot mix asphalt subject to wheel load test

Abstract

The objective of this study is to theoretically and experimentally characterize the internal structure in hot mix asphalt (HMA) mixtures. This is important to evaluate how the internal structures made of four different percentages of flat and elongated (F&E) aggregate change HMA's enginering properties in terms of rut depth, particle movement and orientation, and strain. A micromechanical model is developed to explain the behavior of the internal structure in an HMA mix. The experimental procedure relies on capturing images of the surface of an HMA specimen subject to wheel loading. The results demonstrate that the internal structure adjusts itself in the primary zone, reaches a preferred position in the secondary, but becomes stabilized in the tertiary zone. Low percentages of F&E aggregates result in a stable internal structure that could develop stone-on-stone contact and provide a better interlocking mechanism. The strain distribution within an HMA mix is influenced by particle configuration and mastic behavior, and is very localized.