Study of movement of coarse aggregates in the formation process of asphalt mixture in the laboratory

In this paper, attempts have been made to build an equivalent-sphere mathematical model with respect to length, width, and thickness, in order to describe the coarse aggregates of asphalt mixture in the laboratory. The values of diameters calculated separately based on lengths, widths, and thicknesses have been compared to the model with actual values, which were obtained by two-dimensional digital image processing technique. Certain characteristics of movements were observed during the formation process. The results indicate that an increase of compaction time is accompanied by an increase in average diameter of 2D coarse aggregates and its standard deviation. This shows that the rotations of the coarse aggregates and their better packing effect increase with compaction time. The results also imply that there may be a considerable breaking of coarse aggregates between compaction of 40 and 60 times.