Scale demarcation of self-affine surface of coarse aggregate and its relationship with rubber friction

The surface texture of aggregate is extremely related to the functional performance of asphalt pavement. The textures on different wavelength scales make varying contributions to tire-pavement interaction, especially the rubber friction on a rough road surface. This study develops a two-scaling-range approach based on self-affine to demarcate the wavelengths of texture. A piecewise-linear fitting model was established to determine the cut-off wavelengths employed to separate the window-textures by filtering methods. Afterwards, the window-roughness was introduced to characterise the roughness of texture in a specific scale range. The relationship between the window-roughness and the rubber frictions at different slip speeds was analysed using Pearson correlation. As a result, the self-affine approach is excellent to demarcate the scales without loss of similar characteristics of surface texture. The surface texture of aggregate significantly performs a two-scaling-range self-affine characteristic. The two critical wavelength values respectively vary within 0.10–0.25 mm and 1.0–4.0 mm due to the types of aggregates. Moreover, a strong correlation between the friction and the small-scale roughness will gradually decrease with the increasing slip speed. In contrast, the opposite change is obvious on the larger scales. The method provides guidance for determining the corresponding key wavelength ranges of road surface texture under a rubber slip speed.