Improving the meso-structure identification of asphalt mixture using combined neutron and X-ray imaging

The accurate characterization of the internal structure of asphalt mixture is significant to understand its me-chanical behavior. Combining imaging with neutrons and X-rays is beneficial for investigations of asphalt mixture meso-structure as their different attenuation coefficients for the main components of the asphalt mixture. To compensate for the shortcomings of only using X-ray imaging to identify asphalt mixture meso- structure, this study aims to improve the identification of the meso-structure of asphalt mixture using the complementarity of neutron and X-ray tomography. Due to the lack of experience in using neutron imaging to test the asphalt mixture meso-structure, this paper studied the influencing factors of neutron imaging test on asphalt mixture. To obtain the fusion image, a registration method of the neutron image and X-ray image and an acquisition method of fusion image were proposed. The volume fractions and area fractions of three phases (air voids, aggregates and mortar) obtained from the fusion images were compared with those obtained from neutron and X-ray images. The proposed method was validated by comparing the volume fractions computed from im-ages and the actual values. These efforts contribute to improving the identification of the internal meso-structure of asphalt mixture.