Aggregate shape characterization using digital image processing

David Newton Richardson, Missouri University of Science and Technology
Norbert H. Maerz, Missouri University of Science and Technology


This Innovations Deserving Exploratory Analysis (IDEA) project developed and tested a rapid method based on automated digital imaging technology to characterize aggregate shapes. Work in the initial stage focused on developing methods and testing equipment and making control samples for image-based testing. Over 150 aggregate samples, procured from the Missouri Department of Transportation and a private quarry were used for evaluation. The imaging hardware was modified to use backlighting to reduce errors from dark aggregates and upgraded to allow rapid and accurate measurements. The software was also modified to enable particle angularity measurements in terms of curve radius. Control samples of various configurations with known or uniform characteristics were prepared and tested. Image measured flat and elongation ratios were found to be fairly close to matching caliper results and the repeatability of measurements was found to be better than with manual tests. Results also show that image measured angularity can be correlated with void tests. Analysis of flat and elongation measurements as a function of crusher type showed that impact type crushers tended to produce more cubical particles even when rock type is not accounted for.