Polishing Behavior Analysis Of Asphalt Pavement Surface Texture Based On Piecewise Variable Dimension

Polishing of asphalt surface texture and the consequent decreases of pavement skid resistance are the important factors affecting traffic safety.It is of practical significance to represent the texture characteristics of road surface and reveal the polishing evolution mechanism,which can not only guide the design of pavement material selection,but also predict the decline law of surface anti-skid performance according to the characteristics of road surface materials so as to reduce the accident rate.In this paper,two aspects of theoretical analysis and experimental application are carried out.Firstly,the height difference correlation function was introduced with extending the single dimensional fractal to the piecewise variable dimension fractal based on self-affinity of surface texture,and the piecewise variable dimensional fractal function was fitted in three sections based on the overall error minimization criterion.Secondly,the basalt and the limestone having respectively high and low polished stone value were selected to mold asphalt mixture,the indoor accelerated polishing test was conducted by the plate polishing machine,the dynamic friction coefficient in different polishing cycle were measured.Finally,the 3d laser scanner was used to obtain the specimen surface texture information in the process of polishing,characteristic parameters of profile were calculated,which compared with the friction coefficient.The polishing evolution mechanism was analyzed form two aspects of geometric characteristic parameters and fractal parameters with variable dimension.Research results indicates that: asphalt pavement surface has piecewise variable dimension fractal characteristics obviously,the height difference correlation function can quantify the micro-texture and macro-texture characteristics of the asphalt mixture surface,and the boundary wavelengths between micro-texture and macro-texture of two pavement surfaces are about 0.4mm.The cut-off wavelength can be the indexes to distinguish general polishing and differential polishing.The horizontal cut-off wavelength corresponds the mean asperity and the vertical cut-off wavelength indicates the mean height of the aggregate;With the increase of polishing cycles,the horizontal cut-offwavelength of specimen(basalt)surface texture which affected by the two polishing mechanism changes little,while both cut-off wavelength are down significantly of specimen(limestone)which affected by only the general polishing.In the design and construction process,the aggregate which have more mineral composition,more wide particle size distribution,more hardness large difference between mineral aggregate,are more easily affected by two polishing mechanism,so as to keep enough asphalt surface texture,and delay the skid resistance performance attenuation rate.