Fractal and Multifractal Characteristics of 3D Asphalt Pavement Macrotexture: Fid-Bau Portal

Fractal and Multifractal Characteristics of 3D Asphalt Pavement Macrotexture

Miao, Yinghao / Song, Pingping / Gong, Xiuqing

Pavement macrotexture is a major factor that influences surface functions. This work characterizes the fractal and multifractal properties of asphalt pavement macrotexture using three-dimensional (3D) measurements. A handheld 3D laser scanner is introduced to scan pavement macrotexture in situ. It is verified that the 3D scanning method has good repeatability. Field tests are conducted at 37 highway and urban road sections, which include six types of asphalt pavement surfaces, dense asphalt concrete (DAC), stone matrix asphalt (SMA), rubber asphalt concrete (RAC), ultrathin wearing course (UTWC), microsurfacing (MS), and open graded friction course (OGFC). Three indicators are selected to capture the fractal and multifractal properties of pavement macrotexture: (1) fractal dimension ( $D$ ); (2) the differences between the two endpoints of multifractal spectrum in horizontal; and (3) vertical directions [ $Δ α$ and $Δ f (α)$ ]. These indicators can quantify the general irregularity, the steepness difference between the flattest parts and the steepest parts, and the difference in total area between the flattest parts and the steepest parts of pavement macrotexture, respectively. The correlation coefficients between $D$ , $Δ α$ , $Δ f (α)$ and the mean texture depth (MTD) are 0.8423, 0.7620, and 0.8732, respectively. The correlation coefficient between $Δ f (α)$ and friction coefficient at the speed of $60 km / h$ (DFT60) is 0.6996. It is 0.6639 when relating $D$ and DFT60. However, when relating MTD to DFT60, it is only 0.4483. It is shown that $Δ f (α)$ and $D$ derived from 3D measurement have some advantages over MTD in skid resistance evaluation. The fractal and multifractal indicators enriched the options for macrotexture evaluation.