A Study On Image-based Parameter Characterization Of 3D Morphology Of Asphalt Pavement Coarse Aggregates And On Their Adhesion

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 explore a fast,accurate and quantitative method for 3D morphological parameter characterization of coarse aggregates,3D point cloud data of pebbles,granite and basalt were obtained by using 3D laser scanning technology and processed for analysis.In order to further study the three-dimensional morphology characterization of coarse aggregate of combination of Laplace smoothing and fitted ellipsoid algorithms was then applied to process the models.The values of each parameter of the 3D morphological characterization were calculated and the variation patterns of the multi-characteristic parameters of the three different materials were analyzed.Studies found that the relationship between the long semiaxis,middle semiaxis and short semiaxis of the fitted ellipsoid allows the classification of the coarse aggregate shapes,of which the cubic shape accounts for the most.The angularity of coarse aggregates was evaluated comprehensively by fitting ellipsoid value and the change rate of angularity,among which the angularity of granite was more prominent.According to data fitting analysis,it was found that the fitted ellipsoid could not characterize both the shape and the angularity of the coarse aggregate.The texture of coarse aggregate was evaluated by surface area change rate,and it was found that the surface area change rate of basalt was the most prominent.And the comparison of different grain sizes found that the smaller the grain size was,the more complex and the rougher the surface was.In order to investigate the adhesion relationship between asphalt and aggregate in depth,this research used photoelectric colorimetric method combined with the morphological parameters of coarse aggregate to quantitatively analyze degree of strip of asphalt.Asphalt-coarse aggregate adhesion experiment was conducted based on the photoelectric colorimetric method to calculate the degree of strip of six types of asphalt-coarse aggregates.After the analysis,it can be found that the correlation between the coarse aggregate topography parameters,especially the texture characteristics and the asphalt spalling degree is obvious,but the correlation between the shape parameters and the angular properties is not strong.And it is found that the coarse aggregate with smaller particle size has better adhesion.Through experiments and investigations,it is found that the coarse aggregate with smaller particle size is embedded in the pores of the coarse aggregate with larger particle size,and the texture characteristics are protected.This study provides help for future research on aggregate-asphalt adhesion mechanism and aggregate morphology characterization to promote the development of asphalt pavement design.