Morphological character of coarse aggregate and its influence on high-temperature shear strength of asphalt mixture

The high-temperature shear strength of asphalt mixture was confirmed by using uniaxial penetration test at 60 ℃. The 2D morphological characters of coarse aggregate were described in terms of shape, angularity and surface texture by using digital image processing technology. The gradation of coarse aggregate was identified based on equivalent ellipse method and sieve size correction factor. The morphological characters of coarse aggregate were extracted by MATLAB, and some characters affecting the high-temperature shear strength of asphalt mixture were proved. Euler number of image in digital topology was applied to quantify the skeleton stability of coarse aggregate. Analysis result shows that the shear strength of asphalt mixture increases due to coarse aggregates with low aspect ratio and eccentricity, high angularity index of equal ellipse perimeter and surface texture parameter. As Euler number decreases, the skeleton structure of coarse aggregate in asphalt mixture with dense framework structure becomes steadier, which leads to higher high-temperature shear strength of asphalt mixture.