Internal structure characterization of asphalt concrete using x-ray computed tomography.

Abstract: This study is carried out to develop the workflow from image acquisition to numerical simulation for asphalt concrete (AC) microstructure. High resolution computed tomography (CT) images are acquired and the image quality is improved using digital image processing (DIP). Non-uniform illumination which results in inaccurate phase segmentation is corrected by applying an illumination profile to correct the background and flat-fields in the image. Distance map based watershed segmentation is used to accurately segment the phases and separate the aggregates. Quantitative analysis of the microstructure is used to determine the phase volumetric relationship and aggregates characteristics. The results of the phase reconstruction and internal structure quantification using this procedure shows a very high level of reliability. Numerical simulations are carried out in Two dimensions (2D) and Three dimensions (3D) on the processed AC microstructure. Finite element analysis (FEM) is used to capture the strength and deformation mechanisms of the AC microstructure. The micromechanical behaviour of the AC is investigated when it is considered as a continuum and when considered as a multi-phase model. The results show that the size and arrangement of aggregates determines the stress distribution pattern in the mix.