Coarse aggregate movements during compaction and their relation with the densification properties of asphalt mixture

Abstract

ABSTRACT Densification properties are closely related to the performance of asphalt mixtures; however, the asphalt mixture’s compaction process has not been investigated sufficiently. This study aims to investigate the movements of coarse aggregates in an asphalt mixture and establish a relation between the movements of coarse aggregates and densification properties of the mixture during gyratory compaction using a novel method. Movements of the coarse aggregates, including displacement and rotational angle, were tracked by marking the particles and the results were analysed. After obtaining the densification parameters from the gyratory compaction curve, the densification properties were correlated with the movements. During gyratory compaction, downward vertical and horizontal displacements of the coarse aggregates were easily generated in the mid-upper and mid-lower parts of the mixture, respectively. With the development of gyrations, the coarse aggregates were moderately displaced by continuous slipping with little rotation. The marked aggregates’ movement was enhanced at a large asphalt binder content or high compaction temperature. The mobility of the coarse aggregate was related to the asphalt mixture’s workability. The rotational angle changed rapidly and gently during the earlier and later gyratory compactions, respectively. The densification properties were closely related to the displacements of the coarse aggregates during gyratory compaction.