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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
OCR for page 7
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.
