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6 CHAPTER 2 Findings Evaluation of Merits and Deficiencies sis test method were selected. The multiple ratio shape analysis of Test Methods provides more detailed measurements in terms of the distri- bution of the dimensional ratio. ASTM D 4791 was selected Information gathered from the literature (summarized in because it is included in the Superpave system although it Appendix D) was used to compare 21 available test methods was described as tedious, labor extensive, and time consuming and identify test methods for further experimental evaluation (16, 17) and it does not identify spherical or rounded particles in this study. The advantages and disadvantages of the test and measure one particle at a time (4, 7). methods are summarized in Table 2. The next group of tests uses one camera to image and The test methods were divided into 11 groups based on evaluate particles. It includes the VDG-40 Videograder, Com- analysis concept, as shown in Table 3. The four indirect meth- puter Particle Analyzer, Micromeritics OptiSizer PSDA, Video ods in the first group rely on packing of aggregates that flow Imaging System (VIS), and Buffalo Wire Works PSSDA. Of through a specific-sized orifice. Uncompacted void content of these methods only the VDG-40 Videograder and Buffalo Wire fine aggregates (also known as Fine Aggregate Angularity [FAA] Works PSSDA were selected for evaluation. The VDG-40 test) and uncompacted void content of coarse aggregates were Videograder was selected because it is capable of analyzing selected for further evaluation because they are widely used and every particle in the sample and it showed good correlation cheaper and easier to use than other tests in the same group. with manual measurements of flat and elongated particles Janoo and Korhonen (1) concluded that the FAA test was the (8, 9). The PSSDA method was selected because of its ability easiest to use when it compared to time index, rugosity, and to analyze particles with a wide range of sizes (from passing particle index. Time index was not selected because it is a time sieve #200 to 1.5 in.). consuming test (1) and was classified as having fair perfor- The Camsizer system uses two cameras to capture images at mance, predictability, precision, and accuracy (2). different resolutions; it evaluates a large number of particles In the second group of tests, a compacted specimen is in the sample as they fall in front of a backlight. Using two exposed to pressure or shear forces. Of these methods, the cameras improves the accuracy of measuring the characteris- CAR test is a relatively new test and has not received enough tics of both coarse and fine aggregates. The system has the evaluation. Chowdhury and Button (3) concluded that the capability of automatically producing the distribution of CAR test method offers much more sensitivity than either particles' size, shape, angularity, and texture. the FAA test or the direct shear test. This method also has The WipShape system uses two cameras to capture images more advantages than the Florida bearing ratio and direct of aggregates passing on a mini-conveyor or on a rotating shear tests; it was selected for evaluation. circular lighting table. This system was selected because it can The percentage of fractured particles in coarse aggregate analyze large quantities of particles in a short time and has the method (ASTM D 5821) was selected because it is currently potential to measure and report various shape factors includ- included in the Superpave system. Rao and Tutumluer (4) ing sphericity, roundness, and angularity (10, 11). described this method as being time consuming, labor intensive, UIAIA uses three cameras to capture images from three and subjective. Also, it was classified in another study as having orthogonal directions and build a 3-D shape of each particle; low prediction and precision, with medium practicality (5). it automatically determines flat and elongated particles, coarse Both the ASTM D 4791 test method for measuring flat and aggregate angularity, coarse aggregate texture, and gradation. elongated coarse aggregates and the multiple ratio shape analy- The use of three images for each particle allows an accurate

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Table 2. Advantages and disadvantages of the testing methods used to measure aggregate characteristics. Estimated Measured Aggregate Test Method Equipment Advantages Disadvantages Characteristics Cost ($) A combination of Simple. Lee et al. (1999a) and Chowdhury and angularity, texture, and Inexpensive. Button (2001) reported that the test does shape. Saeed et al. (2001) selected it to measure not consistently identify angular and the properties of aggregates in unbound cubical aggregates. Also, some fine AASHTO T 304 layers. aggregate with good field performance (ASTM C 1252) Meininger (1998) selected it to measure history did not meet the Superpave Uncompacted Void 250 the properties of aggregates in PCC criteria. Content of Fine pavements. The results are influenced by shape, Aggregate Janoo and Korhonen (1999) angularity, texture, and bulk specific recommended it over time index, gravity. rugosity, and particle index. Used in the current Superpave system. A combination of Simple. The results are influenced by shape, angularity, texture, and Inexpensive. angularity, texture, and bulk specific shape. Kandhal and Parker (1998) selected it to gravity. AASHTO TP56 Uncompacted Void measure the properties of aggregates in 500 asphalt pavements. Content of Coarse Aggregate Meininger (1998) selected it to measure the properties of aggregates in PCC pavements. A combination of Simple. Saeed et al. (2001) classified this test as angularity, texture, and Inexpensive. having fair performance, predictability, shape. precision, and accuracy. ASTM D 3398 Meininger (1998) reported that the results Standard Test have high correlation with the FAA test, Method for Index of which is more practical and easier to use. 400 Aggregate Particle Fowler et al. (1996) reported that the Shape and Texture method does not provide good correlation with concrete performance. Results influenced by bulk properties, shape, angularity, and texture. A combination of Simple. The results are influenced by shape, angularity, texture, and Inexpensive. angularity, texture, and bulk properties. Compacted Aggregate shape. Chowdhury and Button (2001) reported 500 that the CAR test method is more Resistance (CAR) Test sensitive to changes in aggregate characteristics than FAA and direct shear test methods. A combination of Simple. The results are influenced by shape, angularity, texture, and angularity, texture, and bulk properties. shape. Less practical and involves more steps than the FAA test. Florida Bearing 1,000 Operates based on the same concept as Value of Fine the CAR test but requires more Aggregate equipment and time. Lee et al. (1999b) stated that FAA test has better correlation with HMA performance than this test. A combination of Simple. The results are influenced by shape, angularity, texture, and Inexpensive. angularity, texture, and bulk properties. shape. It is based on the same concept as the Rugosity 500 FAA test and the uncompacted voids in coarse aggregates test. However, it requires more time and is less practical than these tests. A combination of Simple. The results are influenced by shape, angularity, texture, and Inexpensive. angularity, texture, and bulk properties. shape. It is based on the same concept as the Time Index 500 FAA test and the uncompacted voids in coarse aggregates test. However, it requires more time and is less practical than these tests. A combination of Simple. Expensive. angularity, texture, and Chowdhury and Button (2001) reported The results are influenced by shape, AASHTO T 236 shape. that the test method has good correlation angularity, texture, mineralogy, and (ASTM D 3080) 10,000 with HMA performance. particle size distribution. Direct Shear Test Nonuniform stress distribution causes discrepancies in the measured internal friction. (continued on next page)

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8 Table 2. (Continued). Estimated Measured Aggregate Test Method Equipment Advantages Disadvantages Characteristics Cost ($) ASTM D 5821 Angularity. Simple. Labor intensive and time consuming. Determining the Inexpensive. Depends on the operator's judgment. Percentages of 0 Used in the current Superpave system. Meininger (1998) classified this method Fractured Particles in as having low prediction, precision, and Coarse Aggregate medium practicality. Shape. Used in current Superpave system. Tedious, labor extensive, time consuming Able to identify large portions of flat to be used on a daily basis (Yeggoni et and elongated particles. al. 1996, Rao and Tutumluer 2000). Flat and Elongated Gives accurate measurements of particle Limited to test only one particle at a time. Coarse Aggregates 250 dimension ratio. Unable to identify spherical, rounded, or ASTM D 4791 Found to be related to performance of smooth particles. unbound pavement layers (Saeed et al. Doesn't directly predict performance 2001). (Meininger 1998, Fowler et al. 1996). Shape. Simple. Does not address angularity or texture. Multiple Ratio Shape Inexpensive. 1,500 Analysis Provides the distribution of dimensional ratio in aggregate sample. Shape. Measures the shape of large aggregate Expensive. quantity. Does not address angularity or texture. VDG-40 Weingart and Prowel (1999) and Assumes idealized particle shape Videograder 45,000 Tutumluer et al. (2000) reported good (ellipsoid). correlation with manual measurements of Uses one camera magnification to flat-elongated particles. capture images of all sizes. Shape. Measures the shape of large aggregate Expensive. quantity. Does not address angularity or texture. Computer Particle Analyzer CPA 25,000 Assumes idealized particle shape (ellipsoid). Uses one camera magnification to capture images of all sizes. Shape. Measures the shape of large aggregate Expensive. quantity. Does not address angularity or texture. Micromeritics 50,000 Assumes idealized particle shape OptiSizer PSDA (ellipsoid). Uses one camera magnification to capture images of all sizes. Shape. Measures the shape of large aggregate Expensive. quantity. Does not address angularity or texture. Video Imaging 60,000 Assumes idealized particle shape System (VIS) (ellipsoid). Uses one camera magnification to capture images of all sizes. Shape. Measures the shape of large aggregate Expensive. Angularity. quantity. Assumes idealized particle shape Camsizer 45,000 Uses two cameras to capture images at (ellipsoid). different magnifcations based on aggregate size. Shape. Measures the shape of large aggregate Expensive. Angularity. quantity. Does not address texture. WipShape 35,000 Measures the three dimensions of Uses same camera magnification to aggregates. capture images of all sizes. Shape. Measures the shape of large aggregate Expensive. University of Illinois Aggregate Image 35,000 Angularity. quantity. Uses same camera magnification to Analyzer (UIAIA) Texture. Measures the three dimensions of capture images of all sizes. aggregates. Shape. Measures the three dimensions of Expensive. Angularity. aggregates. Aggregate Imaging 35,000 Texture. Uses a mechanism for capturing images System (AIMS) at different resolutions based on particle size. Gives detailed analysis of texture. Laser-Based Shape. Measures the three dimensions of Expensive. Aggregate Analysis 25,000 Angularity. aggregates. Use the same scan to analyze System Texture. aggregates with different sizes. Note: Prices listed are estimates based on information from users and vendors.