Effect of 3D roughness characteristics on bonding behaviors between concrete substrate and asphalt overlay

Abstract

Asphalt overlay on cement concrete pavement is a common strategy in pavement maintenance. On the other hand, an asphalt layer is generally paved on a concrete bridge deck to provide competitive performance. In this study, the bonding performance between concrete substrate and asphalt overlay was explored from a perspective of interface roughness. Concrete slabs with a strength grade of C50 were fabricated first. Asphalt concretes were paved with an air void content of 4%. The roughness parameters, including surface roughness, root mean square of roughness, and fractal dimension, were obtained from image technique and surface reconstruction. Relationships between surface roughness parameters and direct shear strength were quantitatively studied. The correlation between roughness parameters and optimal tack coat application rate was also built. Results show that the surface roughness linearly increased with the fractal dimension. Larger surface parameters, which was demonstrated as the surface roughness, root mean square of roughness and fractal dimension, contributed to a superior shear performance. Optimal tack coat application rates existed for all specimens. With the increase of surface roughness parameters, the optimal tack coat application rates increased as well. On the other hand, the cohesion strength and internal friction derived from Mohr–Coulomb theory are affected by the roughness parameters of substrates.