Image-Based Coarse-Aggregate Angularity Analysis and Evaluation

The angularity of coarse aggregates significantly influences the performance of asphalt pavement. However, the research remains in the qualitative stage, and no universal evaluation standard has been proposed. This research proposes image-based methods to quantitatively analyze the angularity of coarse aggregates, thereby providing corresponding evaluation standards. First, aggregate levels of 4.75-9.5, 9.5-13.2, and 13.2-16 mm were obtained by sieving experiments, which were then abraded 0, 400, 800, and 1,200 times using a Los Angeles abrasion machine. Subsequently, the aggregate particle angularity parameters, including circumference, area, convex hull circumference, convex hull area, and total number of corner points, were calculated. Meanwhile, the aggregate imaging system (AIMS) gradient, skeleton extraction, convex hull, and uncompacted void content (UVC) methods were used to evaluate the angularities of the aggregates. Thereafter, the AC-13C-type mixture test specimens were formed using different angularity aggregates. On this basis, the angularity-related pavement skid resistance and rut resistance tests were conducted. The results show that the skeleton extraction method performs excellently for evaluating all aggregate levels, while the convex hull method is suitable for 9.5- and 13.2-mm aggregates, the AIMS gradient method is suitable for assessing 4.75- and 9.5-mm aggregates, and the UVC method is suitable for assessing 9.5- and 13.2-mm aggregates.