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8 CHAPTER 3- INTERLABORATORY TEST RESULTS AND ANALYSIS 3.1 Test Data The maximum density and optimum moisture content test data are provided in Table B-1 and Table B-2 of Appendix B. Empty cells in the tables indicate that the laboratory did not submit data. Twenty-one laboratories submitted full sets of data for coarse-graded blends (CC and CS). Twenty-two laboratories submitted full sets of data for fine-graded blend with clay (FC) and twenty-three laboratories submitted full sets of data for the fine graded blend with silt (FS). The maximum dry density and optimum moisture content and their corresponding error bands are displayed in Figure 3-1 and Figure 3-2. It is indicated from the figures that the amount of error in determining maximum density is much smaller than the amount of error in determining optimum moisture content. 110 120 130 140 150 160 170 180 1 3 5 7 9 11 13 15 17 19 21 23 M ax im im D en si ty , l b/ cu ft Lab Number Coarse w/ Clay 110 120 130 140 150 160 170 180 1 3 5 7 9 11 13 15 17 19 21 23 M ax im im D en si ty , l b/ cu ft Lab Number Coarse w/ Silt 110 120 130 140 150 160 170 180 1 3 5 7 9 11 13 15 17 19 21 23 M ax im im D en si ty , l b/ cu ft Lab Number Fine w/ Clay 110 120 130 140 150 160 170 180 1 3 5 7 9 11 13 15 17 19 21 23 M ax im im D en si ty , l b/ cu ft Lab Number Fine w/ Silt Figure 3-1. Maximum density values (lb/cu ft) and their corresponding error bands
9 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 1 3 5 7 9 11 13 15 17 19 21 23 O pt im um W at er C on te nt , % Lab Number Coarse w/ Clay 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 1 3 5 7 9 11 13 15 17 19 21 23 O pt im um W at er C on te nt , % Lab Number Coarse w/ Silt 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 1 3 5 7 9 11 13 15 17 19 21 23 O pt im um W at er C on te nt , % Lab Number Fine w/ Clay 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 1 3 5 7 9 11 13 15 17 19 21 23 O pt im um W at er C on te nt , % Lab Number Fine w/ Silt Figure 3-2. Optimum Moisture Contents (%) and their corresponding error bands 3.2 Method of Analysis Test results of the ILS were analyzed for precision in accordance to ASTM E 691[4]. Prior to the analysis, any partial sets of data were eliminated by following the procedures described in E691 in determining repeatability (Sr) and reproducibility (SR 3.3 Precision Estimates ) estimates of precision. Data exceeding critical h and k values were eliminated from the analysis, where, as described in E 691, the h-statistic indicates the between-laboratory consistency and the k-statistic indicate the within-laboratory consistency of the measurements. Once identified for elimination, the same data were eliminated from any smaller subsets analyzed. Precision estimates of maximum density and optimum moisture content were determined after eliminating the outlier data. One set of data were eliminated from the maximum density and 2 sets of data were eliminated from the moisture content analysis based on the exceedance of the computed from critical h- and k-statistics. The eliminated data are shown shaded in Table B-1 and Table B-2 of Appendix B and are shown in Figure 3-3 and Figure 3-4. All remaining data were re-analyzed according to E691 method to determine the Sr and SR precision estimates shown in Table 3-1 and Table 3-2.
10 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 1 3 5 7 9 11 13 15 17 19 21 23 h Lab Number Coarse w/ Clay h critical -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 1 3 5 7 9 11 13 15 17 19 21 23 h Lab Number Coarse w/ Silt h critical -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 1 3 5 7 9 11 13 15 17 19 21 23 h Lab Number Fine w/ Clay h critical 0.0 0.5 1.0 1.5 2.0 2.5 1 3 5 7 9 11 13 15 17 19 21 23 k Lab Number Coarse w/ Clay k critical 0.0 0.5 1.0 1.5 2.0 2.5 3.0 1 3 5 7 9 11 13 15 17 19 21 23 k Lab Number Coarse w/ Silt k critical 0.0 0.5 1.0 1.5 2.0 2.5 1 3 5 7 9 11 13 15 17 19 21 23 k Lab Number Fine w/ Clay k critical 0.0 0.5 1.0 1.5 2.0 2.5 1 3 5 7 9 11 13 15 17 19 21 23 k Lab Number Fine w/ Silt k critical -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 1 3 5 7 9 11 13 15 17 19 21 23 h Lab Number Fine w/ Silt h critical Figure 3-3. h and k consistency statistics of maximum density from ILS
11 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 1 3 5 7 9 11 13 15 17 19 21 23 h Lab Number Coarse w/ Clay h critical -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 1 3 5 7 9 11 13 15 17 19 21 23 h Lab Number Coarse w/ Silt h critical -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 1 3 5 7 9 11 13 15 17 19 21 23 h Lab Number Fine w/ Clay h critical 0.0 0.5 1.0 1.5 2.0 2.5 1 3 5 7 9 11 13 15 17 19 21 23 k Lab Number Coarse w/ Clay k critical 0.0 0.5 1.0 1.5 2.0 2.5 1 3 5 7 9 11 13 15 17 19 21 23 k Lab Number Coarse w/ Silt k critical 0.0 0.5 1.0 1.5 2.0 2.5 1 3 5 7 9 11 13 15 17 19 21 23 k Lab Number Fine w/ Clay k critical 0.0 0.5 1.0 1.5 2.0 2.5 1 3 5 7 9 11 13 15 17 19 21 23 k Lab Number Fine w/ Silt k critical -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 1 3 5 7 9 11 13 15 17 19 21 23 h Lab Number Fine w/ Silt h critical Figure 3-4. h and k consistency statistics of optimum moisture content from ILS
12 Table 3-1. Summary of Statistics of maximum dry density (lb/cu. ft.) from ILS Sample Type # of Labs Average S CV % x Repeatability (Sr Reproducibility (S) R 1s ) d2s 1s d2s Coarse Aggregate w/Clay 21 147.7 1.71 1.16 0.81 2.26 1.89 5.34 Coarse aggregate w/ Silt 21 147.3 1.68 1.14 0.74 2.06 1.83 5.17 Fine Aggregate w/ Clay 22 139.0 1.54 1.11 0.74 2.08 1.71 4.83 Fine Aggregate w/ Silt 23 138.5 1.52 1.09 0.62 1.73 1.63 4.62 Table 3-2. Summary of Statistics of optimum moisture content (%) from ILS Sample Type # of Labs Average S CV % x Repeatability (Sr Reproducibility (S) R 1s ) d2s 1s d2s Coarse Aggregate w/Clay 21 4.5 0.42 9.41 0.34 0.94 0.49 1.38 Coarse aggregate w/ Silt 21 5.0 0.46 9.28 0.28 0.80 0.55 1.54 Fine Aggregate w/ Clay 22 5.9 0.58 9.91 0.33 0.93 0.50 1.41 Fine Aggregate w/ Silt 23 5.9 0.41 6.96 0.27 0.74 0.41 1.15 3.4 Tests for Significance Tests of statistical significance on the ILS data were performed using t-test and F- test. All t-tests assumed a one-tailed t distribution for 5% level of significance. The t-test was to determine if the difference in maximum density and optimum moisture content of various blends were statistically significant. The F-test was to determine if Sr and SR 3.4.1 Maximum Dry Density precision estimates of the properties for different blends were significantly different. The results of tests for statistical significance on the averages and standard deviations of properties of the four blends are shown in Table 3-3 through Table 3-6 and are discussed in the following sections. 3.4.1.1 Comparison of the Average Maximum Dry Densities The results of t-test on average maximum density values are provided in Table 3-3 . The comparison of computed and critical t values for 5% level of significance indicates that the average maximum density of the fine-graded blends is significantly smaller than those of coarse-graded blends. However, the maximum densities of the blends with the same gradation but different fillers (clay or silt) are not significantly different. 3.4.1.2 Comparison of the Variability of Maximum Dry Density The results of F-test on variances of maximum density are shown in Table 3-4.
13 The comparison of the computed and critical F values for 5% level of significance indicates that there is no significant difference in either Sr or SR Table 3-3. t-values on comparison of the average maximum dry densities of the blends in the ILS estimates of maximum dry density of the coarse-graded and fine-graded blends. The variability of the results from the blends with clay and silt were also not significantly different as indicated by the F values in the table. Therefore, the precision estimates for maximum dry density of the four blends can be combined. Compare Degrees of Freedom Critical t Computed t Decision Coarse w/ Clay & Coarse w/ Silt 40 1.687 0.75 Accept Coarse w/ clay & fine w/ Clay 41 1.688 17.54 Reject Coarse w/ Silt & Fine w/ Silt 42 1.687 18.18 Reject Fine w/ Clay & Fine w/ Silt 43 1.686 0.96 Accept Note: The critical t values are for 95% level of confidence for one tailed test. Table 3-4. F-value on comparison of variability of maximum density of the blends in the ILS Compare Degrees of Freedom Critical F Computed F (S Decision r) Computed F (S Decision R) Coarse w/ Clay & Coarse w/ Silt 20 & 20 2.17 1.21 Accept 1.07 Accept Coarse w/ clay & fine w/ Clay 20 & 21 2.18 1.90 Accept 1.74 Accept Coarse w/ Silt & Fine w/ Silt 20 & 22 2.10 1.91 Accept 1.26 Accept Fine w/ Clay & Fine w/ Silt 21 & 22 2.08 1.45 Accept 1.09 Accept Note: The critical F values are for 95% level of confidence for one tailed test. 3.4.2 Optimum Moisture Content 3.4.2.1 Comparison of the Average Optimum Moisture Content The results of the t-test on optimum moisture content are shown in Table 3-5. The comparison of the computed and critical t values for 5% level of significance indicates that the optimum moisture content of fine-graded blends is significantly higher than that of coarse graded blends. Also shown from the results of t-test, the optimum moisture content of the coarse blend with silt is significantly greater than that of the coarse blend with clay. However, the average optimum moisture content of the fine blends with silt and clay were not significantly different. This could be due to presence of other filler
14 types (limestone dust from sand) in the fine-grained materials. Table 3-5. t-values on comparison of average optimum moisture content of the blends in ILS Compare Degrees of Freedom Critical t Computed t Decision Coarse w/ Clay & Coarse w/ Silt 40 1.687 3.76 Reject Coarse w/ clay & fine w/ Clay 41 1.688 8.81 Reject Coarse w/ Silt & Fine w/ Silt 42 1.687 6.90 Reject Fine w/ Clay & Fine w/ Silt 43 1.686 0.38 Accept Note: The critical t values are for 95% level of confidence for one tailed test. 3.4.2.2 Comparison of the Precision Estimates of Optimum Moisture Content The results of F-test on precision estimates of optimum water content are shown in Table 3-6. The comparison of computed and critical F values for 5% level of significance indicates that there is no significant difference in either Sr or SR Table 3-6. F-values on comparison of variability of optimum moisture content of the blends in ILS estimates of optimum moisture content of the coarse-graded and fine-graded blends. The variability of the results from testing the silt and clay blends were also not significantly different as indicated by the computed F values in the table. Therefore, the optimum moisture content precision estimates of the four blends can be combined. Compare Degrees of Freedom Critical F Computed F (S Decision r) Computed F (S Decision R) Coarse w/ Clay & Coarse w/ Silt 20 & 20 2.17 1.69 Accept 1.52 Accept Coarse w/ clay & fine w/ Clay 20 & 21 2.18 1.39 Accept 1.04 Accept Coarse w/ Silt & Fine w/ Silt 20 & 22 2.10 1.14 Accept 1.81 Accept Fine w/ Clay & Fine w/ Silt 21 & 22 2.08 1.54 Accept 1.01 Accept Note: The critical F values are for 95% level of confidence for one tailed test.
15 3.5 Precision Estimates based on the ILS data Table 3-7 provides the repeatability and reproducibility precision estimates for maximum density and optimum moisture content measurements of the soil-aggregate blends in the ILS. Since the variability of the measurements were not significantly different for the different blends as was indicated by the F-test, the standard deviations were combined to prepare the 1s and d2s limits for single-operator and multilaboratory precisions in Table 3-7. Table 3-7. Precision estimates of maximum density and optimum moisture content from ILS Condition of Test and Test Property 1s d2s Maximum Unit Weight (lbf/ft3 ) Single-Operator Precision 0.73 2.06 Multilaboratory Precision 1.77 5.00 Optimum Water Content (percent) Single-Operator Precision 0.31 0.86 Multilaboratory Precision 0.49 1.39
