Analysis of Segregation Tendency of Aggregates Based on Composite Geometric Characteristics

Abstract

Aggregate segregation is an important factor affecting the early distress and durability of asphalt pavement. To analyze the segregation tendency of aggregates on the mesoscopic scale, first, the segregation tendency of the particle system was measured using an aggregate segregation machine and compared with that of an aggregate-asphalt system. Then composite geometric indexes were calculated and a contact-slip test conducted. The effect of composite geometric characteristics of coarse aggregates on the contact and friction properties of particles was analyzed. Finally, the relations of the segregation index and mesoscopic parameters, including composite geometric indexes and contact-friction indexes, were respectively discussed. The results show that the composite angularity index exhibits a good linear correlation with the segregation index. A larger composite angularity index and composite texture index imply a stronger contact-friction strength of the particle system, which leads to the segregation of coarse aggregates. Fine aggregates move through voids among the coarse aggregates during the falling process. A larger composite shape index indicates more air voids among coarse aggregates, and fine aggregates easily move through voids at higher speed. The bonding/lubrication properties of asphalt can effectively reduce the segregation degree of aggregates.