Research on Characterization of 3D Morphology of Coarse Aggregate Based on Laser Scanning

The morphology of coarse aggregate has a significant impact on the road performance of asphalt mixtures and aggregate characterization studies, but many studies were based on the two-dimensional morphology of coarse aggregate, which failed to consider morphological characteristics in a holistic manner. In order to quantitatively analyze the shape, angularity, and texture characteristics of roadway coarse aggregates, a rapid and accurate multiparameter characterization method of coarse aggregate 3D morphology is explored in this article. A 3D laser scanner is used to obtain the 3D point cloud data of pebble, granite, and basalt, and the solid models of the three coarse aggregates are reconstructed. In addition, the fitted ellipsoidal algorithm and Laplace smoothing algorithm are proposed for the characterization analysis of the overall shape, angularity, and surface roughness of coarse aggregate, and the variation rules of multicharacteristic parameters of coarse aggregate are summarized. The results of the study show that the ratio of the three axes of the fitted ellipsoid can be used to classify the shape of coarse aggregate into four types, among which the cubic shape accounts for the majority of the coarse aggregate. By analyzing the fitted ellipsoidal value and the change rate of angularity of coarse aggregate, it is concluded that the larger the values of both, the more angular the aggregate is. Moreover, the study finds that the fitted ellipsoidal value can characterize not only the shape of coarse aggregate, but also its angularity to some extent. Compared with the spherical value, the fitted ellipsoidal value has better variability and is more “sensitive” to the overall data. The change in surface area can well characterize the texture of coarse aggregate. When the particle size is small, the larger the surface area change rate of the coarse aggregates, the better the roughness of the aggregates, among which the surface area change rate of basalt is the largest. The influence of aggregate morphology was not adequately considered in previous studies of asphalt-aggregate adhesion, and this study provides parameter help for subsequent quantitative analysis of the relationship between asphalt-aggregate adhesion and coarse aggregate morphology.