Evaluation of aggregate gradation and distributing homogeneity based on the images of asphalt mixture

In order to quantitatively evaluate aggregate gradation and distributing homogeneity in asphalt mixture, digital image processing techniques were used to obtain the two-dimensional gradation characteristics in several cross-sections of the coring specimen, and the stereoscopy theory was applied to reconstruct the three-dimensional gradation characteristics, which was compared with the actual gradation, and a correction factor was deduced. It is found that the relative error between corrected and actual aggregate gradation is less than 5%. Then, the aggregated distributing information in horizontal and vertical sections were analysed to establish the horizontal and vertical distributing homogeneity indexes, respectively. The horizontal distributing homogeneity can be evaluated by the variation of inertia of the X-axis, Ix, during rotating, and the vertical distributing homogeneity can be evaluated by the statistical index of the aggregate centroids, Sa. The smaller the Ix variation, the better the horizontal distributing homogeneity. The larger the Sa, the better the vertical distributing homogeneity.