Index of Asphalt Mixture Homogeneity Based on Digital Image Processing

Homogeneity is one of the most important factors affecting the performance-related properties of asphalt mixture. Pavement condition surveys have shown various patterns of distresses due to segregation and other types of non-uniformity. Most of test methods used at present to evaluate asphalt mixture homogeneity have limitations and their test results usually have errors. 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 classify the index of homogeneity, and (3) to examine the main influence factors of the index of homogeneity. The available methods for evaluating asphalt mixture homogeneity, or segregation were reviewed. The digital image processing was concisely introduced. The method for evaluating homogeneity of a cross section in asphalt mixture was described in detail. The method for evaluating homogeneity of the whole was also presented by the index of homogeneity. The classification of the index of homogeneity was listed and discussed. In the end, the main influence factors of the index of homogeneity were quantitatively analyzed. The research results indicate that based on digital image processing it is feasible to quantitatively evaluate asphalt mixture homogeneity through the index of homogeneity which is determined by the aggregate distributed situation, the aggregate distributed number, the area ratio coefficient, and a gradation-related coefficient; 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.