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Investigation of the impact of aggregate segregation on rutting resistance of asphalt concrete

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2019
Yücel, Ayhan Öner
In this study, effect of aggregate segregation on rutting resistance of asphalt concrete is investigated using laboratory compacted specimens. A procedure to determine inhomogeneity level is proposed using 2-dimensional cross section images of asphalt concrete specimens. A redistribution algorithm is developed to assess the aggregate distribution characteristics and inhomogeneity index of the cross sectional images. In order to simulate field conditions, specimens are produced in two different groups: (i) with the same compaction effort and (ii) at the same density corresponding to 4% air void. Unbiased and segregated specimens at two levels are produced for each group using the Superpave gyratory compactor. Repeated creep test is conducted to measure rutting resistance of specimens. Digital images are then produced using a flatbed scanner from the vertical cut sections taken at midpoint of the test specimens. Generated images are processed and analyzed for the analysis of aggregate distribution to compute the specimens’ inhomogeneity levels. The prepared specimens are classified according to their inhomogeneity test results as homogenous, medium level segregated and high level segregated. A number of parameters characterizing the rutting performance of specimens are calculated and the results are statistically analyzed for possible relationships with the inhomogeneity level of the test specimens. Results of statistical analyses show that flow number and loading cycles at 5% permanent deformation are highly correlated with the computed inhomogeneity levels. The outcomes of the study indicate that aggregate segregation significantly affects the rutting resistance of asphalt concrete specimens and the proposed image based method can successfully determine the inhomogeneity level of specimens.