Precision Estimates of AASHTO T 304, AASHTO T 96, and AASHTO T 11 and Investigation of the Effect of Manual and Mechanical Methods of Washing on Sieve Analysis of Aggregates (2014) / Chapter Skim
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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Responsible Senior Program Officer: Edward T Harrigan May 2014 C O N T E N T S Chapter 1 -- Introduction and Research Approach, 1 1.1 Background, 1 1.2 Problem Statement, 2 1.3 Research Objectives, 2 1.4 Scope of Study, 2 Chapter 2 -- Design and Conduct of the Study, 3 2.1 Testing Programs, 3 2.2 Test Methods, 3 2.3 Test Data, 3 2.4 Round Robin Study Instructions, 6 Chapter 3 -- Test Results and Analysis, 6 3.1 Precision Estimates of AASHTO T 96, T 304, and T 11, 6 3.1.1 AASHTO T 96, 6 3.1.2 AASHTO T 304, 8 3.1.3 AASHTO T 11, 10 3.2 Evaluation of the Effect of Sample Size on AASHTO T 11 Test Results, 13 3.2.1 Results of the Analysis, 13 Chapter 4 -- Evaluation of the Method of Washing, 14 4.1 Evaluation of Sieve Analysis Results, 14 4.1.1 Analysis of AGC Data, 15 4.1.2 Analysis of AGF Data, 17 4.1.3 Analysis of HMAIO Data, 20 4.1.4 Analysis of HMASE Data, 22 4.2 Evaluation of Degradation from Mechanical Washing, 24 4.3 Effect of Mechanical Washing Duration on Degradation, 29 Chapter 5 -- Conclusions and Proposed Changes to Standard Test Methods, 31 5.1 Summary and Conclusions, 31 5.1.1 Precision Estimates of AASHTO T 96, 31 5.1.2 Precision Estimates of AASHTO T 304, 31 5.1.3 Precision Estimates of AASHTO T 11, 31 5.1.4 Evaluation of the Effect of Sample Size on T 11 Test Results, 32 5.1.5 Comparison of the Method of Washing, 32 5.1.6 Evaluation of Degradation from Mechanical Washing, 32 5.1.7 Effect of Duration of Mechanical Washing on Degradation, 32 5.2 Proposed Changes to AASHTO Standard Test Methods T 96, T 304, and T 11, 32 References, 33 Unpublished Appendixes, 34 Appendix E, 34 PRECISION ESTIMATES Of AASHTO T 304, AASHTO T 96, AND AASHTO T 11 AND INvESTIgATION Of THE EffECT Of MANUAl AND MECHANICAl METHODS Of WASHINg ON SIEvE ANAlySIS Of AggREgATES This digest summarizes key findings of research conducted in Task Order #2 of NCHRP Project 10-87, "Precision Statements for AASHTO Standard Methods of Test," by the AASHTO Materials Reference Laboratory under the direction of the principal investigator, Dr.
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2Moreover, AASHTO T 11 allows use of mechanical apparatus for the washing operation, provided the results are consistent with those obtained from the manual washing method. The consistency of the results of the two washing methods has not been evaluated.
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3c. Statistically compare the average and standard deviation of the percent passing various sieve sizes resulting from manual and mechanical washing.
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Test Method PSP Tesng Program PSP Sample No. AASHTO T 304 Fine Aggregate (AGF)
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5Test Method PSP Aggregate Type Sample Size PSP Sample No. AASHTO T 11 Materials Finer Than 75 µm (No.
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6test methods according to which the materials were tested, and the dates the data were collected. Table 2-1 shows the sample round numbers of the AGC testing program used for preparing precision estimates of AASHTO T 96.
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7PSP Sample No.
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8As indicated from the R2 values in the plots, there is a strong relationship between averages and both repeatability and reproducibility standard deviations (R2~ 0.7) , while the correlation between averages and both repeatability and reproducibility coefficients of variation is very small (R2~ 0.07 and 0.27, respectively)
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9PSP Sample No.
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10 from the existing precision estimates that were developed based on the graded standard silica sand as described in ASTM C 778. For the new precision estimates, based on the PSP fine aggregates with uncompacted void content in a range of 42% to 45%, the 1s single-operator standard deviation is 0.33% and the 1s multilaboratory standard deviation is 0.81%.
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11 for developing the existing precision estimates of AASHTO T 11. Figures 3-3 and 3-4 show the relationships between average percent passing sieve No.
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12 y = 0.0925x + 0.0418 R² = 0.4472 0 0.05 0.1 0.15 0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Re pe at ab ili ty Average Repeatability Standard Deviation vs. Average (AASHTO T 11/Coarse Aggregate)
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13 3.2 Evaluation of the Effect of Sample Size on AASHTO T 11 Test Results The new and existing precision estimates of AASHTO T 11 in Table 3-7 for fine aggregates are based on a nominal sample size of 500 g. A 1996 revision of this test method permits the fine aggregate test sample size to be the minimum of 300 g.
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14 are noticeably smaller than those corresponding to 500-g samples. Table 3-10 provides the results of statistical F-test on variance.
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15 4.1.1 Analysis of AGC Data Table 4-1 through Table 4-3 provide the results of a statistical comparison of the averages and repeatability/reproducibility standard deviations of the percent passing various sieve sizes pooled separately from manual and mechanical washing of AGC169170, AGC 173-174, and AGC 177-178 samples. Table 4-1 provides the results of the statistical t-test on average percent passing.
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16 during the mechanical washing, resulting in an increase of smaller particles. The comparison of the variability of the gradation measurements from manual and mechanical washing might explain which phenomenon is more likely.
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17 and the variability associated with 19.0-mm, 9.5-mm, and 4.75-mm sieve sizes is statistically significant. The variability of percent passing the 75-µm sieve for mechanical washing is significantly larger than that for manual washing at both the 1% and 5% levels of significance.
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18 mechanical washing of AGF 171-172, AGF 175-176, and AGF 179-180 fine aggregates. Table 4-4 provides the results of the statistical t-test on average percent passing from manual and mechanical washing of AGF 171-172, AGF 175176, and AGF 179-180 samples.
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19 comparison of the mechanical and manual repeatability standard deviations is shown in Figure 4-3. The results of the statistical F-test on variance for comparison of the reproducibility standard deviations of percent passing various sieve sizes from manual and mechanical washing, pooled from AGF 171-172, AGF 175-176, and AGF 179-180 samples, are provided in Table 4-6.
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20 and reproducibility standard deviations of the percent passing of a majority of sieve sizes. Therefore, it might be concluded that mechanical washing would improve removal of the filler and dust from fine aggregates, compared with the manual washing.
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21 size, the percent passing all sieve sizes from mechanical washing is significantly larger than the percent passing manual washing. The results of the statistical F-test on variance for comparison of the repeatability standard deviations of manual and mechanical washing pooled from HMAIO 19-20, 21-22, 23-24, and 25-26 samples are provided in Table 4-8.
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22 from manual and mechanical washing, pooled from HMAIO 19-20, 21-22, 23-24, and 25-26 samples, are provided in Table 4-9. It is indicated from the table that mechanical washing provided improved reproducibility precision of percent passing of six out of nine sieve sizes.
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23 Sieve Size Average Percent Passing, Manual Average Percent Passing, Mechanical Deg. of Freedom Computed t P Value 12.5 mm 94.90 94.90 211 0 1 9.5 mm 86.70 86.73 205 -0.87 0.383 4.75 mm 60.30 60.37 194 -2.03 0.044 2.36 mm 38.20 38.20 233 0 1 1.18 mm 24.67 24.73 228 -1.25 0.214 600 µm 17.17 17.23 231 -1.21 0.228 300 µm 12.83 13.07 218 -4.11 5.625E-05 150 µm 10.50 10.77 213 -4.56 8.765E-06 75 µm, Total 9.07 9.23 213 -2.9 0.004 Note: Critical t for 1% level of significance is 2.59 and for 5% level of significance is 1.97.
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24 the 300-µm sieve and smaller suggests that better washing of aggregates would occur from mechanical washing. The results of the statistical test of significance for individual sample pairs of HMASE 73-74, 75-76, and 77-78 samples can be found in Appendix I
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25 0 0.2 0.4 0.6 0.8 1 1.2 12.5 mm 9.5 mm 4.75 mm 2.36 mm 1.8 mm 600 µm 300 µm 150 µm 75 µm, Total St an da rd De vi ati on s Sieve Size Manual Mechanical figure 4-8 Reproducibility standard deviations of percent passing various sieve sizes after manual and mechanical washing, pooled from HMASE 73-74, 75-76, and 77-78 samples. Sample ID Sieve Sizes % Retained Manual % Retained Mechanical %Loss/ %Gain %Degrada on AGF 171 172 4.75 mm 0.2 0.1 0.1 0.30 2.36 mm 14.3 14.3 0 1.18 mm 14.3 14.3 0 600 µm 18.4 18.5 0.1 300 µm 34.4 34.2 0.2 150 µm 13.6 13.7 0.1 75 µm total 3.1 3.2 0.1 Pan 1.7 1.7 0 AGF 175 176 4.75 mm 14.1 13.8 0.3 0.40 2.36 mm 15.2 15.4 0.2 1.18 mm 18.6 18.6 0 600 µm 31.9 31.8 0.1 300 µm 18.62 18.75 0.13 150 µm 1.2 1.2 0 75 µm total 0.08 0.08 0 Pan 0.3 0.37 0.07 AGF 179 180 4.75 mm 14.1 13.88 0.22 0.32 2.36 mm 14.69 14.78 0.09 1.18 mm 19.6 19.5 0.1 600 µm 31.39 31.41 0.02 300 µm 15.84 15.91 0.07 150 µm 3.19 3.23 0.04 75 µm total 0.14 0.16 0.02 Pan 1.05 1.13 0.08 Table 4-13 Percent degradation of fine aggregates from mechanical washing.
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26 Sample ID Sieve Sizes % Retained Manual % Retained Mechanical %Loss/ %Gain %Degrada on AGC 169 170 25.0 mm 0.2 0.2 0 0.6 19.0 mm 13.8 13.7 0.1 12.5 mm 33.6 33.5 0.1 9.5 mm 37.9 37.5 0.4 4.75 mm 12.1 12.3 0.2 75 µm washing 1.2 1.3 0.1 Pan 1.2 1.5 0.3 AGC 173 174 19.0 mm 13.6 13.5 0.1 0.3 12.5 mm 35 34.8 0.2 9.5 mm 34.4 34.5 0.1 4.75 mm 16.5 16.61 0.11 75 µm washing 0.24 0.25 0.01 Pan 0.26 0.34 0.08 AGC 177 178 19.0 mm 14.8 14.8 0 0.1 12.5 mm 37.7 37.6 0.1 9.5 mm 33.4 33.4 0 4.75 mm 13.66 13.66 0 75 µm washing 0.26 0.3 0.04 Pan 0.18 0.24 0.06 Table 4-14 Percent degradation of coarse aggregates from mechanical washing. HMAIO, and HMASE samples.
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27 Sample ID Sieve Sizes % Retained Manual % Retained Mechanical %Loss/ %Gain %Degrada on HMAIO 19 20 12.5 mm 5.8 5.8 0 0.4 9.5 mm 9.2 9.2 0 4.75 mm 22.3 22.2 0.1 2.36 mm 19.1 19 0.1 1.18 mm 16 16 0 600 m 11 10.9 0.1 300 m 6.2 6.1 0.1 150 m 2.75 2.77 0.02 75 m, Total 1 1.01 0.01 Pan 6.65 7.02 0.37 HMAIO 21 22 12.5 mm 4.4 4.5 0.1 0.5 9.5 mm 6.6 6.5 0.1 4.75 mm 27.4 27.3 0.1 2.36 mm 22 21.9 0.1 1.18 mm 12.6 12.6 0 600 m 7.6 7.6 0 300 m 4.9 4.8 0.1 150 m 2.9 2.8 0.1 75 m, Total 1.9 2 0.1 Pan 9.7 10 0.3 HMAIO 23 24 12.5 mm 5.6 5.6 0 0.5 9.5 mm 10.2 10.1 0.1 4.75 mm 24.5 24.5 0 2.36 mm 25 24.8 0.2 1.18 mm 13.2 13.2 0 600 m 6.2 6.3 0.1 300 m 3.7 3.6 0.1 150 m 2.1 2 0.1 75 m, Total 1.3 1.4 0.1 Pan 8.2 8.5 0.3 HMAIO 25 26 12.5 mm 5.5 5.4 0.1 0.5 9.5 mm 7.8 7.8 0 4.75 mm 26.8 26.8 0 2.36 mm 20.7 20.5 0.2 1.18 mm 12.9 13 0.1 600 m 8.4 8.2 0.2 300 m 4.8 4.8 0 150 m 2.7 2.7 0 75 m, Total 1.7 1.7 0 Pan 8.7 9.1 0.4 Table 4-15 Percent degradation of ignition oven aggregates from mechanical washing.
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28 than the multilaboratory d2s for percent passing various sieve sizes provided in AASHTO T 27 or AASHTO T 30. Therefore, from a practical point of view, the amount of degradation of these aggregates resulting from mechanical washing is not significant.
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29 could be used for evaluation of other samples of the same aggregate type. 4.3 Effect of Mechanical Washing Duration on Degradation The degradation values computed in the previous section were the average values resulting from various mechanical washing durations.
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30 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 1 5 6 10 11+ Pe rc en tE ro sio n (% ) Washing Duration Range (minutes)
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31 CHAPTER 5 -- CONClUSIONS AND PROPOSED CHANgES TO STANDARD TEST METHODS 5.1 Summary and Conclusions This digest was prepared for Task Order #2 of NCHRP Project 10-87 to update precision estimates of three test methods pertaining to aggregate materials: T 96, Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Testing Machine; T 304, Uncompacted Void Content of Fine Aggregate; and T 11, Materials Finer Than 75-µm (No.
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32 estimates are based on fine aggregates having 1.0% to 3.0% finer than the 75-µm (No.
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33 precision estimates are based on the properties of a greater variety of coarse aggregates with a wider range of degradation resistance than those used for developing the precision estimates of ASTM C 131.
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34 6. AASHTO, Designation T 30, "Mechanical Analysis of Extracted Aggregate," Standard Specifications for Transportation Materials and Methods of Sampling and Testing, 32nd Edition, AASHTO, Washington, D.C., 2012, CD-ROM.
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35 the difference in the two results, expressed as a percent of their mean, exceeds the values given in Table E-1, Column 3. E.1.1.2 Multilaboratory Precision (Reproducibility)
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36 the two results, exceeds the values given in Table E-3, Column 3. E.3.1.2 Multilaboratory Precision (Reproducibility)
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Transportation Research Board 500 Fifth Street, NW Washington, DC 20001 These digests are issued in order to increase awareness of research results emanating from projects in the Cooperative Research Programs (CRP)
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