(Replacement for Report No.650 – issued March 2010)
ACKNOWLEDGMENTS
PTA wishes to gratefully acknowledge the technical assistance provided for this program by Mr J Angus of Golder Associates Pty Ltd. This assistance included
preparation, distribution and homogeneity testing of the sample, along with input into the design of the program, technical advice and discussion in the final report.
CONTENTS Page 1. Foreword 1 2. Features of the program 1 3. Format of appendices 2 4. Statistical design of the program 2
5. Outlier results 3
Table A – Summary Statistics 3 Table B – Outlier Results 4
6. Technical Comments 5
Table C - Particle Size Distribution Upper and Lower Limits 6 7. References 7 APPENDIX A – Summary of Results and Robust Z-score Charts
Material finer than 75 µm (nearest 0.1%) A1 – A3
Flakiness Index (nearest whole number) A4 – A6
Particle Size Distribution (nearest whole number) A7 – A14
Average Least Dimension - direct measurement, nominal size 10mm and greater (nearest 0.1mm) A15 – A17
Average Least Dimension - Calculation by Nomograph (nearest 0.1mm) A18 – A20
Particle Shape by Proportional Caliper (nearest 1%) A21 – A24
Particle Density on a Saturated-Surface-Dry Basis (nearest 0.01t/m3) A25 – A27
Apparent Particle Density (nearest 0.01t/m3) A28 – A30
Particle Density on a Dry Basis (nearest 0.01t/m3) A31 – A33
Water Absorption (nearest 0.1%) A34 – A36
APPENDIX B Sample Preparation and Homogeneity Testing B1 APPENDIX C Instructions to Participants and Results Sheet C1 – C2
1
1. FOREWORD This report summarises the results for round six of a series of proficiency testing
programs on the analysis of aggregate.
Proficiency Testing Australia (PTA) conducted the exercise in December 2009 - January 2010. The Program Coordinator was Mr R Sultan. The aim of the program was to assess laboratories' ability to competently perform the tests examined.
2. FEATURES OF THE PROGRAM a) A total of 74 laboratories comprising of 67 Australian and seven overseas participants
(including Cypress and Hong Kong) received samples for this program. A total of 59 facilities returned results in time for inclusion in the final report.
b) Participating laboratories were supplied one bucket of 20mm graded blend of aggregate. c) The following tests were performed on each sample:
• Material finer than 75 µm (nearest 0.1%) • Flakiness Index (nearest whole number) • Particle Size Distribution (nearest whole number) • Average Least Dimension - direct measurement, nominal size 10mm and greater
(nearest 0.1mm) • Average Least Dimension - Calculation by Nomograph (nearest 0.1mm) • Particle Shape by Proportional Caliper at 2:1 and 3:1 ratio (nearest 1%) • Particle Density on a Saturated-Surface-Dry Basis (nearest 0.01t/m3) • Apparent Particle Density (nearest 0.01t/m3) • Particle Density on a Dry Basis (nearest 0.01t/m3) • Water Absorption (nearest 0.1%)
Not all laboratories reported results for each analyte. d) Prior to distribution, the samples were analysed for homogeneity. Based on the results of
this testing it was concluded that the samples were sufficiently homogeneous. Therefore, any results later identified as outliers could not be attributed to any significant sample variability (Appendix B).
e) Laboratories were requested to perform the tests according to their routine methods and
the "Instructions to Participants", and to record their results on the accompanying "Results Sheet", both of which were distributed to participants with the sample
(Appendix C). Each laboratory was randomly allocated a unique code number for the program to enable confidentiality of results. Reference to each laboratory in this report is made by its code number.
2
3. FORMAT OF APPENDICES
APPENDIX A Appendix A lists all the results reported by the participating laboratories for each test.
Calculated robust z-scores, z-score charts and a table of robust statistics - number of results, median, normalised interquartile range (IQR), robust coefficient of variation (CV), minimum, maximum and range, are presented for the following tests: • Material finer than 75 µm • Flakiness Index • Average Least Dimension - direct measurement, nominal size 10mm and greater • Average Least Dimension - Calculation of Nomograph • Particle Density on a Saturated-Surface-Dry Basis • Apparent Particle Density • Particle Density on a Dry Basis • Water Absorption The number of results, median and normalised IQR are presented for the following tests: • Particle Size Distribution • Particle Shape by Proportional Caliper
No z-scores were calculated for Particle Size Distribution and Particle Shape by Proportional Caliper. Upper and lower limits were determined by multiplying the normalised IQR by 3 then adding or subtracting this result from the median. Results reported outside of these limits are classed as outlier results. Scatter plots display the distribution of results reported. Calculated upper and lower limits (median ±3 * IQR) can be above 100% or below 0% which is why scatter plots are used for these tests. Scatter plots are used to set more realistic upper and lower limits i.e. within zero to 100%.
APPENDIX B Appendix B contains details of sample preparation and homogeneity testing data. APPENDIX C Appendix C contains a copy of the “Instructions to Participants” and the “Results Sheet” supplied to participants.
4. STATISTICAL DESIGN OF THE PROGRAM
Robust statistical procedures were used to generate the z-scores and summary statistics for the results, including: • number of results; • median; • normalised IQR; • robust CV; • minimum; • maximum; and • range.
3
Robust z-scores were calculated for each laboratory based on the results submitted for each test. Robust z-scores were not calculated for Particle Size Distribution or Particle Shape by Proportional Caliper. Outliers were determined by setting upper and lower limits.
5. OUTLIER RESULTS In order to achieve the program's aim of assessing laboratories' testing performance, a
robust statistical approach, which uses z-scores to assess participants performance has been utilised. The z-score is a measure of how far the result(s) is from the consensus value - a normalised value which gives a "score" to each result relative to the other results in the group. Therefore a z-score close to zero means that the result agrees well with those from other laboratories. An outlier will be any result(s) which has an absolute z-score value greater than three. For Particle Size Distribution and Particle Shape by Proportional Caliper, any results reported that are outside the upper and lower limits are deemed outliers.
TABLE A: Summary Statistics
Test No. of Results Median Normalised IQR
Material finer than 75 µm (nearest 0.1%) 49 0.90 0.22
Flakiness Index (nearest whole number) 48 11.0 2.2
Particle Size Distribution (nearest whole number)
26.5mm 59 0.0 0.0
19.0mm 59 27.0 4.4
13.2mm 59 63.0 3.0
9.5mm 59 7.0 1.3
6.7mm 58 1.0 0.0
4.75mm 58 0.0 0.6
2.36mm 59 0.0 0.2 Average Least Dimension-direct
measurement ≥ 10mm (nearest 0.1mm) 33 13.30 0.67 Average Least Dimension-Calculation by
Nomograph (0.1mm) 35 13.40 0.44 Particle Shape by Proportional Caliper
(nearest 1%)
2:1 35 13.0 3.7
3:1 36 1.0 1.4 Particle Density on a Saturated-Surface-
Dry Basis (nearest 0.01t/m3) 51 2.570 0.007
Apparent Particle Density (nearest 0.01t/m3) 51 2.630 0.007
Particle Density on a Dry Basis (nearest 0.01t/m3) 51 2.540 0.015
Water Absorption (nearest 0.1%) 51 1.50 0.15
4
* Note for Table A: the data for Particle Size Dist ribution is based on the calculated percent (%) retained for each sieve. Laboratories who reported outliers are listed in Table B. Any laboratories reporting outliers are encouraged to investigate the cause/s of the outlier.
TABLE B: Outlier Results
Test Lab Code
Material finer than 75 µm 6, 21 and 29
Flakiness Index (nearest whole number) none
Particle Size Distribution (nearest whole number)
26.5 outliers not calculated
19.0 47
13.2 none
9.5 none
6.7 3, 4, 32, 40, 57 and 70
4.75 none
2.36 49
Average Least Dimension - direct measurement ≥ 10mm (nearest 0.1mm) 6, 39 and 44
Average Least Dimension - Calculation by Nomograph (0.1mm) 30 and 32
2:1 = 4, 30, 52, 64 and 65 Particle Shape by Proportional Caliper (nearest 1%) 3:1 = 64, 65 and 67
Particle Density on a Saturated-Surface-Dry Basis (nearest 0.01t/m3)
10, 15, 27, 29, 34, 51, 67, 68, 70 and 71
Apparent Particle Density (nearest 0.01t/m3) 15, 27, 29, 31, 34, 68 and 71
Particle Density on a Dry Basis (nearest 0.01t/m3) 10, 15, 27, 34, 51, 67, 68, and 71
Water Absorption (nearest 0.1%) 32, 67 and 71
5
6. TECHNICAL COMMENTS General Comments
Overall, participating laboratories performed the required tests at an average level. For the ten major tests, the 59 participating laboratories reported a total of 851 results. A total of 52 outlier results were reported by 59 laboratories. This means 6.11% of the total results reported for this program were outlier results. This figure has increased when compared to Aggregates round 5 results, where the total percentage of outlier results was 4.12%. Any laboratory reporting results with an absolute z-score between 2 and 3 are also encouraged to review their procedures. Most participants used Australian Standards, however a number of participants also used other standards. Material finer than 75 µm (nearest 0.1%) Three outliers were reported for this test. The percentage of outliers for the Material finer than 75 µm test is 6.1% which is a little lower than 6.9% that occurred in Aggregates 5. Flakiness Index Out of 48 laboratories, only one received a z-score between 2 and 3. There were no outliers reported for this test. Most laboratories performed very well. Particle Size Distribution (nearest whole number) Upper and lower limits were set for each sieve size, with any results outside these limits considered outliers. Scatter plots (see Appendix A) highlight the upper and lower limits and display the spread of results. The statistics for this test were performed on the individual % retained on each sieve size. This was performed for better statistical accuracy. The nature of the sample indicated the majority of aggregate retained was in the 19.0mm and 13.2mm sieves, both having a median of 27% and 63% retained, respectively. 26.5mm : All laboratories reported 0% retained. Statistics could not be performed on this sieve size, therefore no outliers were reported for this test. 19.0mm, 13.2mm and 9.5mm : For the 19.0mm sieve, based on the calculations median + 3 * norm IQR and median - 3 * norm IQR, the upper and lower limits would be 40.3 and 13.7 respectively, however it is considered that the range for acceptable results does not lie within these calculated limits. It is of some concern that there is such a wide range of results (26.6% spread) for this test. Halving the calculated limits based on the program results will equate to a better consensus of results and the median will remain the same. Therefore the upper limit is 33.7 based on median + (3 * norm IQR)/2 and the lower limit is 20.3 based on median – (3 * norm IQR)/2. Only one laboratory received an outlier for these tests and this is considered to be a good result considering the majority of aggregate retained in these sieves. 6.7mm: Six out of the eight outliers in Particle Size Distribution occurred in this sieve. Laboratories reporting a percentage retained outside of 1%, i.e. 2 or higher, received an outlier.
6
4.75mm: The range of acceptable percentage retained results is between 0% to 1.9%. The “Instructions to Participants” indicate reporting to the nearest 1%, therefore any laboratory reporting a percentage retained between and including 0% to 2% did not receive an outlier. No outliers were recorded for this test. 2.36mm: The range of acceptable the percentage retained results is between 0% to 0.7%. The “Instructions to Participants” indicate reporting to the nearest 1%, therefore any laboratory reporting a percentage retained between and including 0% to 1% did not receive an outlier. Only one laboratory received an outlier.
TABLE C: Particle Size Distribution Upper and Lower Limits.
Average Least Dimension - direct measurement nomina l size 10mm and greater This exercise resulted in three outliers out of 33 participants. There is a small spread of z-scores which indicates that most laboratories performed well and reported relatively accurate results. Average Least Dimension - Calculation by Nomograph (0.1mm) There are two outliers out of 35 results (5.71%) for this test. This is an improvement when comparing to Aggregates 5 (8.45%). The results regarding the outliers for this test are satisfactory considering the variables depend on the Particle Size Distribution and Flakiness Index. The outliers the laboratories achieved are totally independent of the method they used e.g. AS1141 or Q202. Particle Shape by Proportional Caliper (nearest 1%) by 2:1 and 3:1 ratio 2:1 ratio: Based on the calculations median + 3 * norm IQR and median - 3 * norm IQR, the upper and lower limits would be 24.1 and 1.9 respectively, however it is considered that the range for acceptable results does not lie within these calculated limits. It is of some concern that there is such a wide range of results (22.2% spread) for this test. Halving the calculated limits based on the program results will equate to a better consensus of results and the median will remain the same. Therefore the upper limit is 18.6 based on median + (3 * norm IQR)/2 and the lower limit is 7.4 based on median – (3 * norm IQR)/2.
7
3:1 ratio: Based on the calculations median + 3 * norm IQR and median - 3 * norm IQR, the upper and lower limits would be 5.1 and 0 respectively. This spread of results is also of some concern, therefore performing the same statistical procedure (i.e. halving the range) as the 2:1 ratio test will equate to a better consensus of results and the median will remain the same. Therefore, the upper limit is 3.1 based on median + (3 * norm IQR)/2 and the lower limit is 0 based on median – (3 * norm IQR)/2. Particle Density on a Saturated-Surface-Dry Basis ( nearest 0.01t/m 3) Ten outliers were reported for this test. Laboratories 15, 27, 34, 68 and 71 also reported outliers in the following two tests. Apparent Particle Density (nearest 0.01t/m 3) Seven outliers were reported for this test and four laboratories received z-scores between 2 and 3. Laboratories that receive a z-score greater than 2 should review their procedures. Particle Density on a Dry Basis (nearest 0.01t/m 3) Eight outliers were reported for this test. The percentage of outliers for this test is 15.7% (8/51) compared to 8.1% (6/74) in Aggregates 5. This is not an improvement compared to the last Aggregates round. Water Absorption (nearest 0.1%)
Three outliers were reported for this test. 7. REFERENCES
[1] Guide to Proficiency Testing Australia (2008).
[2] Australian Standard AS1141.11.1-2009. Methods for sampling and testing aggregates – Particle size distribution - sieving method. [3] Australian Standard AS1141.12-1996. Methods for sampling and testing aggregates – Materials finer than 75 micrometre in aggregates (by washing).
Note: 1 For 19.0mm sieve - The lower limit is calculated by: median – 3 * ½(norm IQR). 2 For 19.0mm sieve - The upper limit is calculated by: median + 3 *½ (norm IQR). 3 For the remaining sieves - The lower limit is calculated by: median – 3 * (norm IQR). 4 For the remaining sieves - The upper limit is calculated by: median + 3 * (norm IQR). 5 § denotes an outlier (i.e. result lies either below the lower limit or above the upper limit).
Note: --- denotes that the laboratory left this space blank
Particle Shape by Proportional Caliper (nearest 1%)
Lab Code 2:1 ratio 3:1 ratio Method
51 12 0 AS1141.14
52 27 § 3 AS1141.14
53 --- --- ---
54 --- --- ---
55 --- --- ---
56 --- --- ---
57 7 0 AS1141.14
58 --- --- ---
60 11 1 AS1141.14
62 --- --- ---
63 --- --- ---
64 80 § 43 § Q213
65 30 § 5 § AS1141.14
66 16 1 --- 67 --- 12 § ---
68 15 1 AS1141.14
69 9 2 AS1141.14
70 --- --- ---
71 15 1 ---
72 --- --- ---
73 --- --- ---
74 12 0 1141.14
No. of Results 35
36
Median 13.0 1.0 Normalised IQR 3.7
1.4
Normalised IQR x 3 11.12
4.11
Upper Limit 18.6 3.1 Lower Limit 7.4 -1.1
Note: 1 For 2:1 and 3:1 - The lower limit is calculated by: median – 3 * ½(norm IQR). 2 For 2:1 and 3:1 - The upper limit is calculated by: median + 3 *½ (norm IQR). 3 § denotes an outlier (i.e. result lies either below the lower limit or above the upper limit).
Note: --- denotes that the laboratory left this space blank
A23
Particle Shape by Proportional Caliper2:1 Ratio (nearest 1%)
14
3111
6928
2423
44
7451
60
30
18 57
1 12
25
26
6
9
3234 38
29
40 71
66
68
3
17
4
52
27
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Laboratory Code Number
Res
ult
A24
Particle Shape by Proportional Caliper3:1 Ratio (nearest 1%)
31
65
52
32
69
556 4426
71
68
666034
38
2412
745728
1191
17 182314
25
27
29
40 5130
3
-1
0
1
2
3
4
5
6
Laboratory Code Number
Res
ult
A25
Particle Density on a Saturated-Surface-Dry Basis ( nearest 0.01t/m 3)
Med 1.50 NIQR 0.15 Robust CV 9.9% Min 1.0 Max 5.4 Range 4.4
Note: § Denotes an outlier
Note: --- denotes that the laboratory left this space blank
A
36
Water A
bsorption(nearest 0.1%
)71
27
12171926283840
53
5758666955
126242944687073
21349141523313447606574
515264
67
32
54
4856
254963
1011
43
-4.0
0
-3.0
0
-2.0
0
-1.0
0
0.0
0
1.0
0
2.0
0
3.0
0
4.0
0
La
bo
rato
ry Co
de
Nu
mb
er
Robust Z-Score
APPENDIX B
Sample Preparation
and
Homogeneity Testing
B1
SAMPLE PREPARATION
A 20mm aggregate was sourced in Queensland. The samples were packaged in 20 litre plastic buckets with handles and tamper proof lids. The sample buckets were numbered sequentially from 1 to 74 in order of preparation. These numbers were independent of the laboratory code numbers.
HOMOGENEITY TESTING Ten numbers were randomly generated and the samples labelled with these numbers were tested for homogeneity. Sieve analysis was conducted according to AS1141.11 and 75 micron by washing was conducted according to AS1141.12. Statistical analysis of the results indicated that no notable sample variability existed. Therefore, it was concluded that any outlier results subsequently identified could not be attributed to sample variability.
INSTRUCTIONS TO PARTICIPANTS Please note, your confidential Lab Code is located on the top right corner of the result sheet. To ensure that results from this program can be analysed properly, participants are asked to adhere carefully to the following instructions. 1. One 15 Kg sample of aggregate has been supplied to each laboratory. 2. Before any testing, mix the sample and then cone and quarter or rifle thoroughly
using the whole sample. 3. The following determinations are to be performed on the sample: Material finer than 75 µm (AS 1141.12) Flakiness Index index (AS 1141.15) Particle Size Distribution (AS 1141.11) on dry sample Average least dimension- direct measurement -nominal size 10mm and greater (AS
1141.20.1) Average least dimension- Calculation – Nomograph (AS1141.20.3) Particle Shape by Proportional Caliper (AS 1141.14) by 2:1 and 3:1 ratio * For the next 4 tests>:Test sieve sizes only above 4.75mm *Particle Density on a Saturated-Surface-Dry Basis (AS 1141.6.1) *Apparent Particle Density (AS 1141.6.1) *Particle Density on a Dry Basis (AS 1141.6.1) *Water Absorption (AS 1141.6.1) 4. These tests are to be conducted in accordance to AS 1141. Laboratories accredited
for performing these tests solely to other methods are required to follow their accredited method and note this on the results sheet.
5. The results for all determinations are to be recorded on the results sheet to the
accuracy and reporting basis indicated. The method used is also to be recorded. 6. Testing may commence as soon as the sample is received. All laboratories must
return the results sheet no later than Friday 18th December 2009 to: Ray Sultan Proficiency Testing Australia PO Box 7507 SILVERWATER NSW 2128 Phone: 02 9736 8397 Fax: 02 9743 6664 Email: [email protected]
C2
PROFICIENCY TESTING AUSTRALIA AGGREGATES PROFICIENCY TESTING PROGRAM
ROUND 6 RESULTS SHEET
Lab Code
TEST (report to)
Result Method
Material finer than 75 µµµµm (nearest 0.1%)
Flakiness Index (nearest whole number)
Particle Size Distribution (nearest whole number)
26.5mm
19.0mm
13.2mm
9.5mm
6.7mm
4.75mm
2.36mm
Average least dimension – direct measurement (nominal size 10mm
and greater)(nearest 0.1mm)
Average least dimension – calculation (Nomograph)(nearest 0.1m)
Particle shape by proportional caliper
(nearest 1%)
2:1 Ratio 3:1 Ratio
*Particle Density on a Saturated-Surface-Dry Basis (nearest 0.01t/m 3)
*Apparent Particle Density
(nearest 0.01t/m 3)
*Particle Density on a Dry Basis
(nearest 0.01t/m 3)
*Water Absorption
(nearest 0.1%)
(*) Only use sample particle sizes above ‘4.75mm’ for tests marked with an asterisk . Date of tests: Signature: Please return to: Ray Sultan, Proficiency Testing Australia
PO Box 7507, Silverwater, NSW, 2128 Fax: 02 9743 6664 By 18th December 2010
