Test Methods for Characterizing Aggregate Shape, Texture, and Angularity (2007) / Chapter Skim
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Appendix A
Appendix A
Pages 51-83
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Disclaimer "The proposed test methods are recommendations of the NCHRP Project 4-30A staff at Texas Transportation Institute. These methods have not been approved by NCHRP or by any AASHTO Committee or formally accepted for the AASHTO specifications." Proposed Test Methods A-1 A P P E N D I X A
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2. Referenced Documents 2.1 ASTM Standards: D 75 Practice for Sampling Aggregates C 136 Test Method for Sieve Analysis of Fine and Coarse Aggregates C 702 Practice for Reducing Samples of Aggregate to Testing Size E 11 Specification for Wire-Cloth Sieves for Testing Purposes 3.
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Shape, angularity, and surface texture of aggregates have been shown to directly affect the engineering properties of highway construction materials such as hot mix asphalt concrete, Portland cement concrete, and unbound aggregate layers. Most methods currently in use for measuring these properties of aggregate particles are indirect Texture Index N D x yn i j j N i A-3= ( )
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Analysis of Coarse Aggregate Angularity, Texture, and Shape 9.1.1. The user must ensure that the objective lens used is 0.25X and that the microscope is placed in the coarse position on the dovetail slide.
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Figure A-1-2. "Analysis Parameters" window for AIMS test setup.
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Clicking this button will cause the microscope to zoom in and achieve maximum magnification. If the point is not clear or not viewable A-6 Test Methods for Characterizing Aggregate Shape, Texture, and Angularity Figure A-1-3.
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Figure A-1-5. "Coarse Aggregate Parameters" window for AIMS test setup.
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If so, click cancel, and place aggregate particles on the tray at the indicated locations. Placement of aggregates can be performed at the beginning, but in that case, the user A-8 Test Methods for Characterizing Aggregate Shape, Texture, and Angularity Figure A-1-6.
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Proposed Test Methods A-9 Figure A-1-7. Calibration point centered at an intermediate magnification.
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Placement of the aggregates begins by placing a translucent sheet (Mylar film) between the aggregate tray and the lighting table, which has an alignment grid indicating the position for 56 particles A-10 Test Methods for Characterizing Aggregate Shape, Texture, and Angularity Figure A-1-9.
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Proposed Test Methods A-11 Figure A-1-11. Aggregate tray with Mylar grid sheet showing proper positions of aggregate particles.
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The system will automatically focus on the top of each aggregate particle and adjust the top lighting. The camera and A-12 Test Methods for Characterizing Aggregate Shape, Texture, and Angularity Don't place aggregates here until camera is set up.
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Proposed Test Methods A-13 Figure A-1-15. Message screen when entering the texture measurement mode.
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A-14 Test Methods for Characterizing Aggregate Shape, Texture, and Angularity Figure A-1-17. AIMS permits processing of all images or only those of a given size.
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Figure A-1-19. Window for selecting one or all aggregate sizes for analysis.
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9.3.1 Analysis of fine aggregates starts by uniformly spreading a few grams of fine aggregate particles on the aggregate tray such that individual particles are not A-16 Test Methods for Characterizing Aggregate Shape, Texture, and Angularity Figure A-1-20. Window for selecting directory type of analysis desired.
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This stepwise process Proposed Test Methods A-17 Figure A-1-22. Example of cumulative distribution for surface texture index.
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. A-18 Test Methods for Characterizing Aggregate Shape, Texture, and Angularity Figure A-1-24.
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9.3.9. Fine aggregate image processing is identical to that for coarse aggregates, except no texture images are acquired.
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9.3.10. Data analysis for fine aggregate is similar to that for coarse aggregate, except the number of analysis parameters (gradient angularity, radius angularity, and 2-D form)
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MRA analysis may be used in the aggregate production process to optimize crusher performance and evaluate product consistency. This method features a new digital flat and elongated measuring device that easily and accurately determines the various coarse aggregate particle shapes found in an aggregate sample.
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Shape of aggregate particles has been shown to directly affect the engineering properties of highway construction materials such as hot mix asphalt concrete, Portland cement concrete, and unbound aggregate layers. Most methods currently in use for measuring these properties of aggregate particles are indirect measurements of the desired properties.
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View of the original prototype multiple ratio analysis system. Figure A-2-2.
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A-24 Test Methods for Characterizing Aggregate Shape, Texture, and Angularity
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This method is intended for simple three-dimensional (3-D) reconstruction of individual coarse aggregate particles for volume, flat and elongated ratio, angularity, and surface texture of coarse aggregate particles.
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shortest dimension, perpendicular to the longest dimension longest dimension Figure A-3-2. The longest and shortest dimensions of a coarse aggregate particle.
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Analysis of coarse aggregate particles includes determining volume, flat and elongated ratio, angularity, and surface texture. The UIAIA features a moving conveyor belt that carries the individual aggregate particle into the view of a sensor, which detects the particle and immediately triggers the cameras.
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Volume, shape, angularity, and surface texture of coarse aggregates have been shown to directly affect the engineering properties of highway construction materials such as hot mix asphalt concrete, Portland cement concrete, and unbound aggregate layers. Most methods currently in use for measuring these properties of aggregate particles are indirect measurements of the desired properties.
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The sizes of the standard specimens chosen are representative of typical coarse aggregate particle sizes encountered in paving applications. Furthermore, the choice of a regular shaped object such as a sphere was made to expedite the calibration process by making it easier to detect and correct measurement irregularities between the different views.
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9.3. Calculation of Coarse Aggregate Size and Shape Properties -- the size and shape indices from the three-camera based aggregate particle reconstruction, i.e., the volume, gradation, flat and elongated ratio, angularity, and surface texture are computed using the algorithms or the virtual instruments (VIs)
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is calculated for each particle in the aggregate sample by clicking on the arrow icon Proposed Test Methods A-31
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Figure A-3-9. Screenshot of user interface or VI for coarse aggregate angularity.
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Proposed Test Methods A-33 Figure A-3-10. Screenshot of user interface or VI for coarse aggregate surface texture.
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