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From page 1... ... Computerized optical methods have been used for quite some time for characterization of fine particles. Several manufacturers of computerized optical equipment have developed applications for measuring the size and shape of translucent glass beads. Read the entire page →
From page 2... ... . This digest summarizes the results of NCHRP Project 20-07, Task 243, as presented in the full project final report titled "Optical Sizing and Roundness Determination of Glass Beads Used in Traffic Markings." The project final report is available as NCHRP Web-Only Document 156 at http://www.trb.org and contains nine appendices: Appendix A, Instructions and Data Sheet for Interlaboratory Study; Appendix B, Results of Percent Retained by Mechanical Sieve; Appendix C, Results of Roundometer; Appendix D, Results of Percent Retained Using COM-A; Appendix E, Results of SPHT Roundness by COM-A; Appendix F, Results of b/l Roundness by COM-A; Appendix G, Results of Size Measurements by COM-B; Appendix H, Results of Roundness by COM-B; and Appendix I, Recommended Test Method for Measurement of Size Distribution and Roundness of Glass Beads Using Computerized Optical Equipment. Read the entire page →
From page 3... ... The laboratories using the computerized optical method were requested to follow instructions prepared with the help of the COM-A and COM-B manufacturers. Participants using the computerized optical method equipment measured percent retained and percent round in each size class of each sample type in terms of the specific parameters of the COM-A and COM-B instruments as presented in Table 3 and Table 4. Read the entire page →
From page 4... ... Analysis of Results from Traditional Mechanical Methods Sieve analysis and roundness measurements using mechanical sieves and the roundometer were conducted following the ASTM D1214 and ASTM D1155 test methods, respectively. The following sections provide the results of the precision and bias analysis of the measurements using the traditional methods. Read the entire page →
From page 5... ... All remaining data were re-analyzed according to the E691 method to determine the repeatability and reproducibility statistics shown in Table 5. As indicated from this table, the measured percent retained agrees relatively well with the target percent retained for all sieve sizes, e.g., measured retained value of 48.4% for #50 sieve agrees well with the 50% target retained value. Read the entire page →
From page 6... ... Measured % Sieve of Round, Sizes Labs Average STD, % CV, % STD, % CV, % #16 6 75.1 1.7 2.3 4.1 5.5 #18 8 78.5 2.3 2.9 4.1 5.2 #20 7 73.9 1.6 2.1 4.7 6.4 #25 7 65.6 12.5 19.0 11.8 18.0 Repeatability Reproducibility Table 7 Statistics of percent retained of Type 5 samples using mechanical sieve shaker No. Target Measured Sieve of % % Retained, Sizes Labs Retained Average STD, % CV, % STD, % CV, % #12 14 5.0 5.2 0.6 12.4 1.0 18.9 #14 13 55.0 58.5 2.2 3.7 4.3 7.4 #16 14 35.0 31.4 2.8 9.0 4.1 13.2 #18 13 5.0 5.0 0.7 14.4 1.2 23.6 Repeatability Reproducibility Read the entire page →
From page 7... ... All remaining data were re-analyzed according to the E691 method to determine the repeatability and reproducibility statistics shown in Table 10. A review of the statistics in the table indicates the roundness of the Type 5 beads was underestimated for all size classes, e.g., the measured percent round of 83.4% for the #14 beads is smaller than the target roundness of 90%. Read the entire page →
From page 8... ... All remaining data were re-analyzed according to the E691 method to determine the repeatability and reproducibility statistics shown in Table 12. A comparison of the measured and target percent retained in Table 12 indicates a good agreement between the measured percent retained and the target percent retained in the #18 size class, which has the largest number of beads. Read the entire page →
From page 9... ... Looking at the percent retained in the size classes with the largest number of beads in the Type 1, Type 3, and Type 5 samples indicates that both accuracy and precision of measurements improved with the coarseness of the glass bead types. Roundness Measurements Using the SPHT Parameter A total of four laboratories reported the percent roundness of the three sample types measured by the SPHT parameter (see Table 3) Read the entire page →
From page 10... ... Summary of Percent Round by COM-A SPHT. The analysis of mass percent round using the COM-A SPHT parameter indicates that the measured percent round in the most prevalent size classes provided closest agreement with the target value. Read the entire page →
From page 11... ... The results in Table 18 further indicate that the repeatability and reproducibility coefficients of variation of percent round according to the b/l parameter for the #18 and #20 beads, which are the most prevalent sizes, are very small. This indicates that b/l is a reliable parameter for measuring the roundness of the most prevalent size classes of Type 3 glass beads. Read the entire page →
From page 12... ... The analysis of D10, D50, and D90 data measured by COM-A indicated that COM-A measured the size distribution of the three types of glass bead samples reasonably well. Only one out of nine 12 Table 20 Comparison of measured and target particle sizes of Type 1 beads for 10%, 50%, and 90% passing Sieve Target Particle No. Read the entire page →
From page 13... ... All remaining data were re-analyzed according to the E691 method to determine the repeatability and reproducibility statistics shown in Table 23. As indicated in the table, the measured and target percent retained values agree relatively well with the target retained values. Read the entire page →
From page 14... ... The measurements in the most prevalent size classes also indicated small repeatability and reproducibility coefficients of variation for Type 1 samples and small coefficient of variation for the Type 3 and Type 5 samples. Roundness Measurements The roundness of the glass beads measured by COM-B was determined based on the T/L parameter described in Table 4. Read the entire page →
From page 15... ... The analysis of mass percent round with the COM-B T/L parameter indicates that the threshold value for the parameter is not the same for all glass bead types. While the threshold value of 0.83 seems adequate for Type 5 glass beads, it did not correctly determine the percent round of Type 1 and Type 3 beads. Read the entire page →
From page 16... ... Mechanical shaking would overcome these forces and separate the beads, while they would likely stay clustered passing through computerized optical equipment. Type 3 Samples The precision estimates for measuring the percent retained in the #18 size class of the Type 3 samples by 16 Table 30 Comparison of measured and target particle size of Type 3 samples for 10%, 50%, and 90% passing Sieve Target Particle No. Read the entire page →
From page 17... ... Summary of Precision in Size Measurement Comparison of the precision estimates for measuring the percent retained in the most prevalent size classes of Type 1, Type 3, and Type 5 glass beads revealed important information about the methods of measurement. For Type 1 samples, the mechanical sieve provided the least within and between variability. Read the entire page →
From page 18... ... Type 3 Samples Precision estimates of the percent roundness in the #18 size class for the Type 3 samples for various methods of measurement are provided in Table 36. The precision estimates are based on the mass percent round of three 100-g Type 3 glass bead replicates measured by participating laboratories. Read the entire page →
From page 19... ... This analysis of bias included a t-test on the size and roundness measurements of the most prevalent size class of each glass bead type. The prevalent size classes are the #50 size class for Type 1 samples, the #18 size class for Type 3 samples, and the #14 size class for Type 5 samples. Read the entire page →
From page 20... ... This suggests that computerized optical equipment is especially suitable for measuring the size distribution of the larger-sized glass beads. Roundness Measurement Tables 41, 42, and 43 summarize the percent round statistics of the three sample types. Read the entire page →
From page 21... ... in Table 42 corresponds to the SPHT parameter, indicating that the measured roundness as judged by this parameter was significantly different from the target roundness. Type 5 Samples Table 43 compares the percent round measurements with the target percent round on the #14 sieve of the Type 5 samples. Read the entire page →
From page 22... ... Analysis of the mass percent retained in the largest size class of the Type 1 samples indicated that of the three methods of measurement, the COM-B device provided the most accurate measurement of the size of Type 1 glass beads. With respect to variability, the mechanical sieve provided the smallest within-laboratory standard deviation for measuring the size of the small beads. Read the entire page →
From page 23... ... Although a smaller number of laboratories provided data using the COM-B device, both size and roundness of the Type 1 glass beads were correctly measured by the COM-B instrument. A draft practice in AASHTO standard format for determining the size and roundness of glass beads utilized in traffic markings using the computerized optical method is provided in Appendix A Read the entire page →
From page 24... ... 2. REFERENCED DOCUMENTS 2.1 AASHTO Standard M 247 Standard Specification for Glass Beads Used in Pavement Markings 2.2 ASTM Standards D1214-04 Standard Test Method for Sieve Analysis of Glass Spheres D1155-03 Standard Test Method for Roundness of Glass Spheres B215-08 Standard Practices for Sampling Metal Powders 2.3 ISO Standards ISO 13322-2 International Standard for Dynamic Image Analysis Method Read the entire page →
From page 25... ... 3.1.5 Image capture device -- Minimum of two digital cameras 3.1.6 Particle illumination unit -- Light source for continuous illumination for image capture device 3.1.7 Sample collection container -- For collecting the glass beads at the end of the test 3.1.8 Particle size analyzer -- A general term for computerized optical equipment 3.2 Description of Terms (See Figure 1) : 3.2.1 Xcmin (particle width) Read the entire page →
From page 26... ... Therefore, there are uncertainties associated with using a single cutoff threshold for all glass bead types. The proposed threshold values for each roundness parameter have been computed as the median over each range of threshold values corresponding to Types 1, 3, and 5 glass beads. Read the entire page →
From page 27... ... Figure 2 provides a schematic diagram of the measurement components of the system. The equipment is structured into a dosage funnel, a vibrating dosage feeder, guide plate, measurements volume, an illumination unit, image capturing device, image analysis software, and sample collection container. Read the entire page →
From page 28... ... Please make sure that all information contained in the material safety data sheets of the analyzed materials is observed. If used in compliance with the operating instructions, the instrument can be operated safely and efficiently. Read the entire page →
From page 29... ... 8.4 Installation location: place the Particle Analyzer on a firm, horizontal, vibration-free surface. 8.5 Light conditions: avoid strong direct external light on the particle measurement shaft or on the cameras. Read the entire page →
From page 30... ... Note 2 -- A reasonable mass tolerance for test specimens is 0.5 g. Table 1 Appropriate mass for various size glass bead types specified in AASHTO M 247 AASHTO Type Range (µm) Read the entire page →
From page 31... ... 11.2 Computerized Optical Equipment Preparation 11.2.1 All measuring and analysis parameters should be determined initially and saved into the pre-defined files referred to as task files or method files. Note 3 -- Check with instrument manufacturer for suggestions on how to best set up any software that comes with the instrument. Read the entire page →
From page 32... ... 11.2.2.11 Select SPHT or NSP for roundness measurement; use a threshold value of 0.93. 11.2.2.12 Choose percent round in each class size based on Xcmin/XFemax (b/l) Read the entire page →
From page 33... ... 4 Value of Xcmin/XFemax (b/l) or T/L for each size classification and the weighted average value for the whole sample 13.1. Read the entire page →
From page 34... ... Two results submitted by two different operators testing the same material in different laboratories shall not be considered suspect unless the difference in the two results exceeds the values given in Table 3, Column 5. Table 3 Precision estimates for percent retained and percent round of Type 1, Type 3, and Type 5 glass beads Type Index and Test Property Standard Deviation (1s) Read the entire page →
From page 35... ... 15. KEYWORDS 15.1 Sieve size; roundness; glass beads; particle size analyzer 16. Read the entire page →
From page 36... ... . Persons wanting to pursue the project subject matter in greater depth should contact the CRP Staff, Transportation Research Board of the National Academies, 500 Fifth Street, NW, Washington, DC 20001. Read the entire page →

From page 1...

... Computerized optical methods have been used for quite some time for characterization of fine particles. Several manufacturers of computerized optical equipment have developed applications for measuring the size and shape of translucent glass beads.