Rapid Test to Establish Grading of Unbound Aggregate Products: Evaluation of Potential Aggregate Grading Technologies
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A research study is underway to develop automated methods for rapidly grading aggregates on the production line in a typical aggregate separation or mixing facility. This interim report serves to document preliminary work on this project and presents: (1) A discussion of typical plant layouts, to identify potential sampling locations. The best sampling locations appear to be just after final screening, where sorted material is sent to stockpiles, and just before mixing the final product, where aggregates are fed from either stockpiles or charge bins. (2) A thorough examination of six potential technologies that could be used to rapidly determine particle size. After a critical review and a formal decision analysis, both digital image analysis and laser profiling appear to be equally promising and worthy of additional study. (3) A discussion of our current thinking on how to configure scanning equipment of this kind. By considering innovative methods for presenting aggregate particles to the scanning sensor, the opportunity exists for advancing this technology. An outline of project work planned for the immediate future. Continuing our study of both digital image analysis and laser profiling, we plan to: 1. Conduct a limited, independent evaluation of three commercial particle-sizing machines, which all use digital image analysis. 2. Perform preliminary tests using a laser profiler. 3. Construct a laboratory test bed that can be used to test and evaluate various scanning sensors.