A Comparison of Optical Gradation Analysis Devices to Current Test Methods ― Phase 1

Optical devices for gradation analysis are being developed to deliver accurate gradation results with, less labor, less consistency error, and greater reliability. The goal of this study was to conduct a review and develop comprehensive understanding of the existing technology for gradation analysis, and generate basic data to determine when and where such devices are appropriate from the standpoint of both economies and performance. Following a review of available optical devices, an optical device called Computerized Particle Analyzer (CPA) was selected for laboratory evaluation to determine its suitability for gradation analysis. This device has been designed to examine particles as they freely fall in front of a light source, while a sophisticated camera capable of making 10,000 scans per second captures images. Aggregate samples were collected from 46 different sources in Ohio. These sources included various sizes of limestone and gravel with varying amounts of crushed faces. Gradation tests were first performed according to the standard American Association of State Highway and Transportation Officials (AASHTO) procedure. The samples were then tested in CPA. Preliminary test results revealed that the CPA device has the potential to produce gradation results comparable to the traditional ASTM and AASHTO procedures. The device is capable of producing consistent and repeatable test data. It is computer-controlled and user-friendly. Two primary benefits noted during the evaluation are: (i) time savings, and (ii) generation of additional information. One gradation test can be completed in less than five minutes, compared to 30 to 60 minutes for the conventional procedure. More importantly, the same data can also be used to obtain additional information about elongation index and angularity. While the results so far show promise, a definitive determination of the suitability of the device for use in Ohio will require further research.


  • English

Media Info

  • Media Type: Print
  • Edition: Final Report
  • Features: Figures; Photos; References; Tables;
  • Pagination: 33p

Subject/Index Terms

Filing Info

  • Accession Number: 01046403
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/OH-2006/23
  • Contract Numbers: 134264
  • Created Date: Mar 31 2007 9:32AM