1. AASHTO TP56. Standard test method for uncompacted void content of coarse aggregate as influenced by particle shape, surface texture, and grading. American Association of State Highway and Transportation Officials, AASHTO TP56-99, Washington, DC; 1999.
2. Innovation of aggregate angularity characterization using gradient approach based upon the traditional and modified sobel operation;Chen;Constr Build Mater,2016
3. Fletcher T, Chandan C, Masad E, Sivakumar K. Aggregate Imaging System (AIMS) for characterizing the shape of fine and coarse aggregates. Transportation Research Record 1832, Journal of the Transportation Research Board, Washington, DC; 2003. p. 67–77.
4. Huang H. Discrete element modeling of railroad ballast using imaging based aggregate morphology characterization. Thesis Submitted to the University of Illinois for the degree of Doctor of Philosophy in Civil Engineering, Urbana, Illinois; 2010.
5. Discrete element modeling for fouled railroad ballast;Huang;Constr Build Mater,2011