Characterization of internal pore size distribution and interconnectivity for asphalt concrete with various porosity using 3D CT scanning images

Abstract

The open pore characteristics of asphalt mixtures play a crucial role in their resistance to water-induced damage. Accurate extraction and analysis of the pore structures at a micro level can reveal the seepage characteristics of asphalt pavements. However, existing studies mainly focus on the through-pore characteristics of porous asphalt mixtures and there is a lack of research on the open pore characteristics and interconnected paths of dense graded asphalt mixtures. This study aims to fill this gap by using 3D X-ray computed tomography technology to analyze the digital images of three typical asphalt mixtures with different porosities. The study quantitatively and statistically analyzes several new pore structure parameters at a micro level, such as porosity, equivalent diameter, coordination number, pore throat dimension, and tortuosity. The interconnected paths of the pores are also compared and analyzed. The results show that as the total pores content increases, the difference between the pore fraction and open pores fraction decreases. The porosity of porous asphalt mixtures is high, but mainly composed of interconnected pores with only a small proportion of closed pores. The coordination number determines the connectivity and thus the porosity of the asphalt mixture, and larger open pore channels lead to larger pore diameters and greater permeability. As the porosity of the asphalt mixture increases, the average coordination number of its internal pores also increases, leading to better pore connectivity and a more complex pore network.