Towards an Index of Asphalt Mixture Homogeneity

Homogeneity is one of the most important factors affecting the performance-related properties of asphalt mixtures. Pavement condition surveys have shown various patterns of distresses due to segregation and other types of non-uniformity. Most of presently used test methods have limitations to evaluate asphalt mixture homogeneity and their test results usually have flaws. The main objective of this research is to investigate the index of asphalt mixture homogeneity using digital image processing, which includes three aspects: (1) to develop the index of homogeneity, (2) to categorize the index of homogeneity, and (3) to examine the main influence factors of the index of homogeneity. By the aggregate distributed situation, the aggregate distributed number, the area ratio coefficient, and a gradation-related coefficient, a method for evaluating homogeneity of a cross section in asphalt mixtures was described in detail, and a method for evaluating the whole homogeneity was also presented. The research results indicate that based on digital image processing it is feasible to quantitatively evaluate asphalt mixture homogeneity through the index of homogeneity; the index of homogeneity can be classified by Empirical-Analytical method; aggregate gradation, asphalt content, compaction effort, and experimental temperature all influence the index of homogeneity.