ASTM D7681-11(2021)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7681 − 11 (Reapproved 2021)
Standard Test Method for
Measuring Gradation of Glass Spheres Using a Flowing
Stream Digital Image Analyzer
This standard is issued under the fixed designation D7681; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1.1 This test method covers the determination of the grada-
2.2 AASHTO Standards:
tion (size distribution) of glass spheres used in pavement
AASHTO M247-08 Standard Glass Beads Used in Traffic
marking systems using a Flowing Stream Digital Analyzer.
Markings
Typical gradations for pavement marking systems are defined
in ranges from Type 0 through 5 in AASHTO M247-08.
3. Terminology
1.2 Thistestmethodprovidesforthepresentationofthesize
3.1 Definitions:
data in a variety of formats to the requirements of the agency
3.1.1 flowing stream digital image analyzer, n—a computer
pavement marking material specification. For most specifica-
controlled particle size analyzer employing a high resolution
tions the standard format is to present the size data as “Percent
digital imaging device and computer image processing soft-
Retained” or “Percent Passing” relative to a series of standard
ware to do photo optical single particle counting and particle
US sieve sizes.
size analysis.
1.3 The values stated in SI units are to be regarded as
3.1.2 gradation of glass beads, n—the measurement of the
standard. No other units of measurement are included in this
size(diameter)ofglassbeadsandtheirsubsequentpresentation
standard.
in ranges between ASTM standard sieve sizes and/or micron
1.4 This standard does not purport to address all of the
designation starting with the largest to the smallest; the ranges
safety concerns, if any, associated with its use. It is the are listed as “percent passing” and “percent retained.”
responsibility of the user of this standard to establish appro-
4. Summary of Test Method
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
4.1 The glass particles are run through a flowing stream
1.5 This international standard was developed in accor-
digital image analyzer, a measuring system for determining the
dance with internationally recognized principles on standard-
gradation (size distribution) of dry, free flowing and harmless
ization established in the Decision on Principles for the
bulk products. The total recommended measuring range is
Development of International Standards, Guides and Recom-
between 100 µm and 2.36 mm. The operating test method uses
mendations issued by the World Trade Organization Technical
photo optical single particle counting technology for the image
Barriers to Trade (TBT) Committee.
processing. The measurement time depends on the quantity of
material to be measured, the width of the metering feeder and
2. Referenced Documents
the mean grain size. The quantity of material to be measured
2.1 ASTM Standards:
depends on the grain size and the width of the metering feeder.
B215 Practices for Sampling Metal Powders Typical measuring times are approximately 2 to 10 min.
E177 Practice for Use of the Terms Precision and Bias in
5. Significance and Use
ASTM Test Methods
5.1 The gradation (size distribution) of glass beads has a
significant influence on the retroreflective efficiency of a
This test method is under the jurisdiction of ASTM Committee D01 on Paint
pavement marking system.
and Related Coatings, Materials, andApplications and is the direct responsibility of
Subcommittee D01.44 on Traffic Coatings.
5.2 This test method is for the characterization of the
Current edition approved Nov. 1, 2021. Published November 2021. Originally
ɛ1
gradation (size distribution) of glass beads for the purpose of
approved in 2011. Last previous edition approved in 2016 as D7681 – 11 (2016) .
DOI: 10.1520/D7681-11R21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available from American Association of State Highway and Transportation
Standards volume information, refer to the standard’s Document Summary page on Officials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,
the ASTM website. http://www.transportation.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7681 − 11 (2021)
compliance testing against standard specification for glass 10. Calibration and Standardization
beads in pavement marking applications.
10.1 The particle analyzer, in most cases, will be calibrated
5.3 While there are potential industrial applications for this by the manufacturer prior to shipping. Re-calibration might
test method beyond the measurement of gradation (size distri- become necessary occasionally, for example, after the trans-
bution) of glass beads for pavement markings, those are portation of the instrument or if required by quality manage-
beyond the scope of this standard. mentregulations.Inthiscase,followthecalibrationprocedures
as outlined in the manufacturer’s instruction manual.
6. Apparatus
11. Conditioning
6.1 Typical Instrument Operating Conditions (Fig. 1):
6.1.1 Environmental Temperature—10 °C.40 °C.
11.1 Sample Preparation:
6.1.2 Air Humidity—80 % maximum relative humidity at
11.1.1 Use a sample splitter, if necessary, to reduce the
temperatures up to 30 °C, linear decrease to 50 % maximum
amount of sample to the appropriate size.
relative humidity at a temperature of 40 °C.
11.1.2 Pour entire glass bead sample into the glass beaker or
6.1.3 Height of Installation and Operation—Maximum suitable container.
3000 m above sea level.
11.1.3 Assure glass beads are moisture free and free flow-
6.1.4 Installation Location—Place the particle analyzer on a ing.
firm, horizontal, vibration free surface.
NOTE 1—Check with instrument manufacturer for suggestions on how
6.1.5 Light Conditions—Avoid strong direct external light
tobestsetupanysoftwarethatcomeswiththeirinstrument.Settingupthe
on the particle measurement shaft or on the cameras.
instrument software properly will speed up any glass sphere gradation
measurements and allow for meaningful reports.
6.1.6 This test method is designed for indoor or outdoor use
as prescribed by the manufacturer’s design and instructions.
12. Procedure
7. Hazards
12.1 Load the sample into the feeder of the flowing stream
digitalimageanalyzer.Theanalyzersoftwareallowstheuserto
7.1 General Safety Information:
7.1.1 Operate the instrument in accordance with the manu- carry out his measurements quickly and without error. All
measuring and analysis parameters are determined initially and
facturer’s recommendations following all required safety pre-
cautions. set into the computer program. Different task files are created
for different specifications.
8. Sampling, Test Specimens, and Test Units
NOTE 2—When assigning sieve ranges to be used in a task file, the user
8.1 Obtain a minimum of approximately 50 6 5 g specimen must use the ASTM mesh sieve choice, not the W. S. Tyler mesh. The
quantity of the material to be measured has to be placed into the funnel of
of the glass beads to be tested for gradation (size distribution).
the metering feeder. The material handling mechanisms must not restrict
For larger sizes of glass spheres, such as Type III and larger,
or segregate product flow in any way that allows for a non-representative
whose gradation is defined inAASHTO M247-08, 75 to 125 g
flow of product through the measurement zone.
samples shall be used.
12.2 After the task file has been defined only a minimal
8.2 In order to obtain representative samples when sam-
number of operative steps are required for carrying out a
pling from packaged containers, blenders or storage tanks,
measurement. They are: (a) filling a quantity of the material to
methods outlined in Practices B215 shall be followed.
be measured into the funnel to the metering feeder, (b) calling
the measurement and choosing the task file, (c) confirming the
9. Preparation of Apparatus
suggested comments or entering new comments, (d) starting
9.1 Follow the manufacturer’s instructions for the particle the measurement, and (e) reading the result or printing a
analyzer being used. record. The measured result is available a few moments after
FIG. 1 Typical Apparatus
D7681 − 11 (2021)
the measurement is completed and can be displayed in many results for the same material, obtained by the same operator
forms, and be printed and saved with the help of the PC. using the same equipment on the same day in the same
laboratory.
13. Report
14.1.2.1 Repeatability limits are listed in Tables 1-12.
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