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Accession Number PB2013-102481
Title Comparison of Optical Gradation Analysis Devices to Current Test Methods-Phase 2. Final Report.
Publication Date Apr 2012
Media Count 109p
Personal Author A. Rajagopal
Abstract Phase-2 was initiated: (i) to validate the gradation results derived from CPA, and (ii) to investigate its suitability for the measurement of shape characteristics of aggregates such as % Fractured Face (ASTM D5821) and Flakiness and Elongation Index (ASTM D4791). The fractured face test is subjective and requires visual inspection of aggregate surface to estimate percent of fractured surface. The CPA device is not configured to directly output this property. However, the device measures another property termed Sphericity. The researchers attempted to establish a correlation between %FF and the Spherecity values. To pursue this goal, a total of 202 aggregate samples (78 gravel and 204 limestone) were tested. Flat and elongated test requires the measurement of largest and least dimension of each particle. A free falling particle always falls with its largest dimension exposed to the camera. However, the width exposed to the camera may not always correspond to the least dimension. This is particularly true for flaky particles which lie on their flat surface. In order to overcome this limitation and to capture the least dimension, the feeder bin was redesigned so as to allow only one particle to fall at a time. The effort culminated in the redesign of feeder so as to allow only one particle to fall at a time.
Keywords Computerized particle analyzer
Computerized Particle Analyzer (CPA)
Existing technology
Gradation analysis
Laboratory evaluation
Optical devices

Source Agency Federal Highway Administration
NTIS Subject Category 46C - Optics & Lasers
49E - Optoelectronic Devices & Systems
50A - Highway Engineering
50C - Construction Equipment, Materials, & Supplies
62 - Computers, Control & Information Theory
Corporate Author Ohio Dept. of Transportation, Columbus. Office of Research and Development.
Document Type Technical report
Title Note N/A
NTIS Issue Number 1303
Contract Number N/A

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