Effects of coarse aggregate morphology on Asphalt mixture’s flowability: Parametric and prediction study

Abstract

Morphological characteristics of aggregates affect the flowability and workability of asphalt mixtures during pavement construction. To quantify the effects of coarse aggregate morphological characteristics on its flow performance, aggregates were artificially smoothened through abrasion to different levels of angularity and then evaluted based on Angle of repose (AOR)tests in laboratory. Moreover, morphological characteristics of aggregates with different sizes were scanned and rebuilt based on Particle Flow Code (PFC). 61 sets of virtual Angle of repose tests were further conducted in order to get statistical results and help to develop a predictive model of aggregates’ flowability. The study results indicate that within the commonly used particle size range of 2.36–13.2 mm in pavement, the larger the particle size, the greater the AOR test results. Within 500 cycles of abrasion, most morphological parameters of aggregates show a clear positive correlation with its flowability. Variables based on the aggregate shape scale (Ellipse ratio and Aspect ratio), and angular scale variables(Circularity and 3D Angularity), can well predict the flowability of aggregates. The significance of their contribution to the flowability are shown as follow: Aspect ratio > 3D Angularity > Circularity > Ellipse ratio. Thus, it is important to control the morphological characteristics of aggregates within a reasonable range in order to improve the flowability and workability of asphalt mixtures during pavement construction phase.

Keywords

• Aggregate morphology
• Discrete element method (DEM)
• Angle of repose (AOR)
• Pavement engineering
• Flowability