This project developed and tested a rapid method based on automated digital imaging technology to characterize aggregate shapes (Fig. 1). A prototype automated imager analyzer (Fig. 1) was developed and evaluated. Over 150 aggregate samples, procured from the Missouri DOT 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. The equipment needs additional development, refinement, and testing for its implementation.  The final report is available from the National Technical Information Service (NTIS # PB2004-105016).

The final report for this IDEA project can be found at:
https://www.trb.org/studies/idea/finalreports/highway/NCHRP078_Final_Report.pdf