Evaluation method for homogeneity of asphalt mixtures based on CT technique

To evaluate the homogeneity of asphalt mixtures effectively, the inner structure of mixtures specimens was identified by using CT technique, and an evaluation method for the mixtures was established by taking specific and area of components of coarse aggregate, asphalt mastics, and air voids as main characteristic parameters, then the homogeneity evaluation indices (K_d and K_z) for single cross section and specimen were presented in the method. The asphalt mixture specimens produced by three different aggregate gradations with each of gradation containing four asphalt contents, were used to evaluate the homogeneity of asphalt mixtures specimens, as well, the fabrication discrepancies in asphalt mixtures specimens were examined. Besides, the optimum asphalt content of asphalt mixture was obtained, and the unsubstantial positions for the homogeneity of inner structures of asphalt mixtures specimens were determined. The results show that the homogeneity of inner structure of single asphalt mixture specimen or a set of asphalt mixtures specimens can be evaluated by the method; the fabrication discrepancy in a set of asphalt mixtures specimens with uniform compaction approach and aggregate gradation can be verified, and the reliability of it in practical use is further proved to be well through the results of splitting test; the asphalt contents corresponding to the optimum homogeneity of inner structure of the asphalt mixtures (AC, SMA, and OGFC) are obtained by using the homogeneity evaluation index (K_z) analysis, and the differences between those values and the optimum asphalt contents achieved by the Marshall test are 0.07%, 0.1%, and 0.55%, respectively, which provides a reference to the optimum asphalt content of asphalt mixtures determined by the Marshall test; the difference between the maximum K_d and the average of K_d for the single cross section of the mixtures specimens can be employed to determine the unsubstantial position for inner structure homogeneity of the specimens.