Abstract: The shape of grains is one of the main factors influencing the structural characteristics of pores in filled breakstone aggregate, subsequently affecting its mechanical and hydraulic properties. Two sets of limestone gravel aggregate with diameters of 2-5 mm and 5-10 mm were investigated using CT scanning technique and graphic software, from which the pore appearance images of the porous media were acquired. Two sets of glass balls that were with the same granular compositions and porosity as those of the two sets of limestone gravel aggregate were made, and the glass ball sets were compared with the limestone gravel aggregate sets in the test. The threshold value of 0.5 mm opening was applied to the segmentation of pore structure. Three section images of each sample were selected so as to quantitatively analyze pore characteristics by means of the average values of quantitative parameters as the research object. The results show that the pore shape in filled glass ball is more complex than that in filled breakstone. The connectivity degree of pore system in filled breakstone is also less than that in glass ball.

Key words: grain shape, pore structure, CT scanning, shape parameter, fractal, connectivity degree