Abstract:

The research on the vertical distribution of air voids of porous asphalt mixture was carried out using XCT technique, digital graphic processing technique and the fractal theory. The results show that the void features images are able to describe the connectivity and distribution characterization of porous asphalt mixture and there is no inplane connectivity in it; the air voids of the six sections studied ranges from 17.7% to 22.2%; the greatest discrepancy of air void quantity among different sections is 16, accounting for about onequarter of the total quantity; all the air void profile fractal dimension are larger than the corresponding air void area fractal dimension, and it has nothing to do with air void quantity. The air void gradation figure shows that the gradations in two orthogonal crosssection mostly distribute within 4~8 mm in the same sample, but with different distributional pattern. The contrastive analysis find that the discrepancy of maximum diameter between transverse air void and vertical air void is 2 mm with relatively close equivalent diameter.

Key words: road engineering, distribution characterization of air voids, X-ray CT technique, porous drainage asphalt mixture