Recommended Precision Statements for AASHTO Standard Methods of Test T22, T 104, T 105, T 154, T 186, and T 242 (2010)

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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Research Results Digest 342 January 2010 INTRODUCTION The objective of NCHRP Project 9-26A is to recommend new or updated precision statements of AASHTO standard meth- ods of test designated by the technical sections of the AASHTO Highway Sub- committee on Materials (HSOM). To meet this objective, NCHRP Project 9-26A uses both data mining techniques and inter- laboratory studies (as defined in ASTM D 6631, Standard Guide for Committee D01 for Conducting an Interlaboratory Prac- tice for the Purpose of Determining the Precision of a Test Method). The project is a continuing, open-ended effort; reports are published in the form of NCHRP Web- Only Documents (WOD) as tasks related to individual standard methods are com- pleted. Precision statements and supporting results are provided to AASHTO HSOM for review and possible adoption. This Research Results Digest summa- rizes the findings of research conducted between January 2007 and June 2009 in Project 9-26A to recommend new or up- dated precision statements of the AASHTO standard methods of test shown in Table 1. These specific precision statements were developed through statistical analysis of multi-year results obtained from (1) the Proficiency Sample Programs (PSP) of the AASHTO Materials Reference Laboratory (AMRL) and the ASTM Cement and Con- crete Reference Laboratory (CCRL) and (2) calibration testing of state friction mea- surement systems at field test centers at the Texas Transportation Institute, College Sta- tion, Texas, and the Transportation Research Center, East Liberty, Ohio. A complete report of the development of each precision statement is presented in the WODs (1, 2, 3, 4) listed in Table 1. FINDINGS Data Sets Precision statements for methods of test T 22, T 154, and T 186 were developed through an analysis of 24 data sets collected from laboratories participating in the phys- ical analysis of hydraulic cement paste and measurement of the compressive properties of hydraulic cement concrete in the CCRL PSP between 2003 and 2007. These data RECOMMENDED PRECISION STATEMENTS FOR AASHTO STANDARD METHODS OF TEST T 22, T 104, T 105, T 154, T 186, AND T 242 This digest summarizes key findings obtained between January 2007 and June 2009 under continuing NCHRP Project 9-26A, “Data Mining and In- terlaboratory Studies to Prepare Precision Statements for AASHTO Standard Test Methods.” NCHRP Project 9-26A was conducted by the AASHTO Materials Reference Laboratory under the direction of the Principal Inves- tigator, Dr. Haleh Azari. This digest is based on task reports co-authored by Dr. Azari and Messrs. Ronald Holsinger, Robert Lutz, and Peter Speller- berg; these task reports are available online as NCHRP Web-Only Documents 139, 140, 141, and 142. Subject Areas: IIIB Materials and Construction Responsible Senior Program Officer: E. T. Harrigan

2sets reflect a wide range of test data for the cement types included in the scope of the CCRL PSP. The precision statement for method of test T 104 was developed through an analysis of six data sets collected from laboratories participating in the analysis of sulfate soundness of coarse and fine ag- gregate in the AMRL PSP between the years 2003 and 2009. The precision statement for method of test T 105 was developed through an analysis of 10 data sets collected from laboratories participating in the chem- ical analysis of hydraulic cement in the CCRL PSP between the years 2003 and 2007. The precision statement for methods of test T 242 was developed through an analysis of friction data collected during the calibration of state friction measurement systems at Texas Transportation Insti- tute and Transportation Research Center field test centers. Two sets of data were analyzed: “Initial” and “Final” as referred to by TTI or “Arrival” and “Departure” as referred to by TRC. The Initial or Arrival set was collected when the state systems arrived at the centers; the Final or Departure set was collected after adjustments were made to the state systems to put them into compliance with ASTM E 274, Skid Resistance of Paved Surfaces Using a Full-Scale Tire, which is equivalent to AASHTO T 242. The TTI Initial and Final data sets consisted, respectively, of 288 friction numbers from 12 run- repeats of 8 state friction measurement systems and 1,260 friction numbers from 12 run-repeats of 12 state friction measurement systems. The TRC Ar- rival and Departure data sets consisted, respectively, of 1,296 friction numbers from 12 run-repeats of 12 state friction measurement systems and 5,400 fric- tion numbers from 12 skids of state friction mea- surement systems in 50 different configurations (left, right, or both wheels with either ribbed, smooth, or both tire types). Data Analysis The PSP data were analyzed with a technique developed by AMRL in Phase 3 of NCHRP Project 9-26 (5). This technique is a four-step procedure for shaving off extraneous results and analyzing the core data of a paired data set. The results of the analysis of the core data can then be used to obtain reliable single-operator and multi-laboratory esti- mates of precision. Analysis of the friction data was based on the method in ASTM E 691, Standard Practice for Con- ducting an Interlaboratory Study to Determine the Precision of a Test Method. Prior to the analysis, partial data sets were eliminated by following the procedures described in ASTM E 691 in determin- ing repeatability (Sr) and reproducibility (SR) esti- mates of precision. Data exceeding critical h and k values were eliminated as described in Section 15.6 of the test method; these same data were also elimi- nated from any smaller subsets analyzed. New Precision Statements and Comparison with Existing Statements AASHTO Standard Method of Test T 22 The 7-day compressive strength of hydraulic cement concrete was analyzed for one set of 4 in. × 8 in. and five sets of 6 in. × 12 in. proficiency sample pairs. Precision estimates are based, where appro- priate, on either the coefficients of variation (CV%) or the pooled standard deviation (1s) values. New criteria developed in this research for judg- ing the acceptability of compressive strengths ob- tained by AASHTO T 22 are given in Table 2. The figures given in the second column of Table 2 are the standard deviations that were found to be appropri- ate for the materials and conditions of test described in the first column of the table. The figures in the third Table 1 Methods of test and web-only documents AASHTO Standard Method of Test NCHRP Web-Only Document T 22, Compressive Strength of Cylindrical Concrete Specimens 140 T 104, Soundness of Aggregate by Use of Sodium Sulfate or Magnesium Sulfate 141 T 105, Chemical Analysis of Hydraulic Cement 139 T 154, Time of Setting of Hydraulic Cement Paste by Gillmore Needles 140 T 186, Early Stiffening of Hydraulic Cement (Paste Method) 140 T 242, Frictional Properties of Paved Surfaces Using a Full-Scale Tire 142

column are the limits that should not be exceeded by the difference between the results of two properly conducted single-operator or multi-laboratory tests. The bias of AASHTO T 22 was not determined be- cause no comparison with a material having an ac- cepted reference value was conducted. Table 3 compares the new and existing precision estimates for AASHTO T 22; the new repeatability and reproducibility standard deviations are larger than the existing precisions. It is not clear if this difference is due to a change in the CCRL reference material or changes in the method of test in the interval between the development of the two sets of precision estimates. AASHTO Standard Method of Test T 104 Six AMRL proficiency data sets that reflect the 1,999 revisions to AASHTO T 104 were analyzed to derive precision estimates. The majority of the data sets represent test results from greater than 100 lab- oratories. The data sets were selected to include a wide range of sodium and magnesium sulfate sound- ness values. Criteria developed in this research for judging the acceptability of percentage loss of coarse and fine aggregates by the sulfate soundness test (AASHTO T 104) are given in Table 4. The figures in the sec- ond column of Table 4 are the coefficients of varia- tion that have been found to be appropriate for the materials and conditions of test described in the first column of the table. The figures in the third column of the table are the limits that should not be exceeded by the difference between the results of two properly conducted single-operator or multi-laboratory tests as a percent of their mean. The bias of AASHTO T 104 was not determined because no comparison 3 Table 2 Precision estimates of compressive strength of cylindrical concrete specimens Condition of Test Coefficient of Variation (1s), Acceptable Range of Two Test Results (d2s), and Test Property Percent of Average* Percent of Average* Single-Operator Precision: 6 × 12 in. (150 × 300 mm) 4.7 13.2 4 × 8 in. (100 × 200 mm) 4.3 12.1 Multi-Laboratory Precision: 6 × 12 in. (150 × 300 mm) 8.1 23.0 4 × 8 in. (100 × 200 mm) 7.6 21.6 *These values represent the 1s and d2s limits described in ASTM Practice C670. NOTE: The precision estimates given in Table 2 are based on the analysis of test results from one pair of 4 in. × 8 in. and five pairs of 6 in. × 12 in. CCRL hydraulic concrete proficiency samples. The data analyzed consisted of results from 267 laboratories for the 4 in. × 8 in. samples and 910 to 1,002 laboratories for each of the 6 in. × 12 in. sample pairs. The analysis included 4 in. × 8 in. samples with an average compressive strength of 3,950 psi and 6 in. × 12 in. samples with an average compressive strength of 3,851 psi to 4,812 psi. Table 3 Comparison of the new and existing precision estimates for AASHTO T 22 Acceptable Range of Coefficient of Variation, Two Test Results, Percent of Mean Percent of Mean Condition of Test and Type Index New Existing New Existing Single-Operator Precision: 6 × 12 in. (150 × 300 mm) 4.7 2.4 13.1 6.6 4 × 8 in. (100 × 200 mm) 4.3 3.2 12.0 9.0 Multi-Laboratory Precision: 6 × 12 in. (150 × 300 mm) 8.1 5.0 22.8 14.0 4 × 8 in. (100 × 200 mm) 7.6 NA 21.4 NA

4with a material having an accepted reference value was conducted. The new and existing precision estimates for AASHTO T 104-99 (2003) are provided in Table 5; the single operator precision of the sodium sulfate soundness procedure was reduced while all other precisions increased in comparison to the existing precisions. However, the repeatability and repro- ducibility coefficient of variations of both new and existing precisions are so large that their utility for within- and between-laboratory comparisons are uncertain. Improving the precisions of the test will require comprehensive ruggedness testing that exam- ines the key variables of the test method. AASHTO Standard Method of Test T 105 Ten AMRL proficiency data sets were analyzed to derive the precision estimates. The majority of the data sets represent test results from more than 100 laboratories. The data sets were selected to include Type I and Type I/II cements with and without lime- stone and Type V cement with limestone. Criteria for judging the acceptability of percent- ages of chemical components that are obtained using AASHTO T 105 for hydraulic cement are presented in Table 6. The figures in the second column of Table 2 are the standard deviations that were found to be appropriate for the chemical components in the first column of the table. Two results obtained in the same laboratory, by the same operator using the same equipment, in the shortest practical pe- riod of time, should not be considered suspect un- less the difference in the two results exceeds the values given in the third column of Table 6. The fig- ures in the fourth column of the table are the multi- laboratory standard deviations that have been found to be appropriate for the chemical components in the first column. Two results submitted by two different operators testing the same material in different lab- oratories should not be considered suspect unless the difference in the two results exceeds the values given in the fifth column. The bias of AASHTO T 105 could not be determined because no comparison with a material having accepted reference values was conducted. A comparison of the new and existing precision estimates for AASHTO T 105-06 showed a signifi- cant improvement in the precision of several of the chemical analyses. This improvement likely results Table 4 Precision estimates for AASHTO T 104 Coefficient of Variation (1s), Difference Between Two Tests (d2s), Material and Type Index Percent of Mean* Percent of Mean* Single-Operator Precision: Coarse Aggregate Sodium Sulfate 19 53 Magnesium Sulfate 18 51 Fine Aggregate Sodium Sulfate 12 35 Magnesium Sulfate 10 27 Multi-Laboratory Precision: Coarse Aggregate Sodium Sulfate 68 190 Magnesium Sulfate 60 168 Fine Aggregate Sodium Sulfate 52 145 Magnesium Sulfate 45 125 *These values represent the 1s and d2s limits described in ASTM Practice C670. NOTE: The precision estimates given in Table 4 are based on an analysis of the weighted average of sulfate soundness loss test results from 60 pairs of AMRL proficiency samples. The data analyzed consisted of results from 90 to 282 laboratories for each of the pairs of samples. The analysis of coarse aggregate sulfate soundness included 19.0-mm to 4.75-mm aggregate with a weighted average sodium sulfate loss of 0.3% to 3.5% and an average magnesium sulfate loss of 0.4% to 14.9%. The analysis of fine aggregate sulfate soundness included 1.18-mm to 300-micron fine aggregate with an average sodium sulfate loss of 1.7% to 2.2% and an average magnesium sulfate loss of 3.3% to 5.21%.

5Table 5 Comparison of the new and existing T 104 precision estimates Coefficient of Difference Between Variation (1s), Two Tests (d2s), Percent Percent of Average Existing Precisions Material and Type Index New Precisions (AASHTO T104-99(2003)) Single-Operator Precision: Coarse Aggregate Sodium Sulfate 19 53 24 68 Magnesium Sulfate 18 51 11 31 Fine Aggregate Sodium Sulfate 12 35 – – Magnesium Sulfate 10 27 – – Multi-Laboratory Precision: Coarse Aggregate Sodium Sulfate 68 190 41 116 Magnesium Sulfate 60 168 25 71 Fine Aggregate Sodium Sulfate 52 145 – – Magnesium Sulfate 45 125 – – Coefficient of Difference Between Variation Two Tests (d2s), (1s), Percent Percent of Average Table 6 Precision estimates for AASHTO T 105 Standard Deviation Acceptable Range of Standard Acceptable Range of (1s)* Two Test Results (d2s)* Deviation (1s)* Two Test Results (d2s)* Chemical Components Single-Operator Precision Multi-Laboratory Precision SiO2 (silicon dioxide) 0.119 0.333 0.196 0.549 Al2O3 (aluminum oxide) 0.073 0.204 0.110 0.308 Fe2O3 (ferric oxide) 0.029 0.081 0.051 0.143 CaO (calcium oxide) 0.199 0.557 0.384 1.075 MgO (magnesium oxide) 0.049 0.137 0.070 0.196 SO3 (sulfur trioxide) 0.047 0.132 0.076 0.213 LOI (loss on ignition) 0.055 0.154 0.085 0.238 Na2O (sodium oxide) 0.013 0.036 0.024 0.067 K2O (potassium oxide) 0.009 0.025 0.016 0.045 TiO2 (titanium dioxide) 0.005 0.014 0.007 0.020 Cl (chloride) 0.002 0.006 0.004 0.011 IR (insoluble residue) 0.048 0.134 0.080 0.224 Free calcium oxide 0.125 0.350 0.214 0.599 CO2 (carbon dioxide) 0.083 0.232 0.219 0.613 * These values represent the 1s and d2s limits described in ASTM Practice C670. NOTE: The precision estimates given in Table 6 are based on the analysis of test results from 107 pairs of CCRL proficiency samples. The data analyzed consisted of results from 66 to 221 laboratories for each of the pairs of samples. The analysis included five cement types: Type I and Type I/II with and without limestone and Type V with limestone.

6from recent advancements in methods for chemical analysis of hydraulic cement. AASHTO Standard Method of Test T 154 The Gillmore initial and final times of setting of hydraulic cement were analyzed for each of six cement paste proficiency sample pairs. Precision estimates are based, where appropriate, on either the coefficients of variation (CV%) or the pooled stan- dard deviation (1s) values. Criteria for judging the acceptability of Gillmore initial and final times of setting obtained by AASHTO T 154 are given in Table 7. The figures given in the second column of Table 7 are the standard devia- tions that have been found to be appropriate for the materials and conditions of the test described in the first column of the table. The figures in the third column of the table are the limits that should not be exceeded by the difference between the re- sults of two properly conducted single-operator or multi-laboratory tests. The bias of AASHTO T 154 was not determined because no comparison with a material having an accepted reference value was conducted. Table 8 compares the new and existing precision estimates for AASHTO T 154; both repeatability and reproducibility statistics are improved, likely due to recent improvements to the test method. AASHTO Standard Method of Test T 186 The early stiffening of hydraulic cement mea- sured with the Vicat apparatus was analyzed for each of six cement paste proficiency sample pairs. Precision estimates are based, where appropriate, on either the CV% or the pooled 1s values. Criteria are given in Table 9 for judging the ac- ceptability of early stiffening of hydraulic cement paste by AASHTO T 186 and expressed as the ratio of the final to initial penetration calculated as a percentage. The figures given in the second column of Table 9 are the standard deviations that have been found to be appropriate for the materials and condi- tions of the test described in the first column of the table. The figures in the third column of Table 9 are the limits that should not be exceeded by the differ- ence between the results of two properly conducted Table 7 Precision estimates of time of setting of hydraulic cement paste by Gillmore needles Acceptable Standard Range of Deviation Two Test Condition of Test (1s), Results (d2s), and Test Property Minutes* Minutes* Single-Operator Precision: Initial Time of Setting 12 34 Final Time of Setting 16 46 Multi-Laboratory Precision: Initial Time of Setting 23 64 Final Time of Setting 37 103 * These values represent the 1s and d2s limits described in ASTM Practice C670. NOTE: The precision estimates given in Table 7 are based on the analysis of test results from 6 pairs of CCRL proficiency samples. The data analyzed consisted of results from 156 to 168 laboratories for each of the pairs of samples. The analysis included cement pastes with an average Gillmore initial time of setting of 139 to 193 min and an average Gillmore final time of setting of 238 to 303 minutes. Table 8 Comparison of new and existing precision estimates for AASHTO T 154 Standard Acceptable Range of Deviation (1s), Two Test Results (d2s), Condition of Test Minutes Minutes and Type Index New Existing New Existing Single-Operator Precision: Initial Time of Setting 12 16 34 44 Final Time of Setting 16 22 46 62 Multi-Laboratory Precision: Initial Time of Setting 22 28 63 78 Final Time of Setting 37 46 104 129

7single-operator or multi-laboratory tests. The bias of the procedure was not determined because no com- parison with a material having an accepted reference value was conducted. Table 10 compares the new and existing preci- sion estimates for AASHTO T 186; both repeata- bility and reproducibility statistics have improved, likely due to the recent improvements in the test method. AASHTO Standard Method of Test T 242 The precision statement for AASHTO T 242 is based on repeatability and reproducibility stan- dard deviations of the final state friction system measurements. The single operator and multi-operator stan- dard deviations (1s limits) for FN (friction number unit) are shown in the second column of Table 11. The results of two properly conducted friction tests on the same surface, by the same operator, and using the same equipment, should be consid- ered suspect if they differ by more than d2s single operator limits shown in the third column of Table 11. The results of two properly conducted tests on the same surface, by different operators, using dif- ferent systems, should be considered suspect if they differ by more than the d2s multi-laboratory limit shown in the third column of Table 11. No information can be presented on the bias of the procedure because no material having an accepted reference value was available. The current version of AASHTO T 242 in- cludes a repeatability standard deviation that can be compared with the repeatability standard devi- ation computed in this study. The repeatability standard deviation is reported as 2 FN in AASHTO T 242-96 (2004), which is significantly larger than the computed repeatability standard deviation of 0.83 FN computed in this study. This difference is likely due to careful calibration of state friction systems during their evaluation at TTI and TRC. Table 9 Precision estimates of early stiffening of hydraulic cement (paste method) Acceptable Range Standard of Two Test Condition of Test Deviation (1s), Results (d2s), and Test Property Percent* Percent* Single-Operator Precision 7 21 Multi-Laboratory Precision 8 24 *These values represent the 1s and d2s limits described in ASTM Practice C670. NOTE: The precision estimates given in Table 9 are based on the analysis of test results from 6 pairs of CCRL proficiency samples. The data analyzed consisted of results from 171 to 210 laboratories for each of the pairs of samples. The analysis included cement pastes with average False Set of 69% to 85%. Table 10 Comparison of the recommended and existing precision estimates for AASHTO T 186 Acceptable Range Standard Deviation of Two Test Condition of Test (1s), Percent Results (d2s), Percent and Type Index New Existing New Existing Single-Operator Precision 7 10 21 28 Multi-Laboratory Precision 8 12 24 34

8REFERENCES 1. Azari, H., R. Holsinger, and R. Lutz, NCHRP Web- Only Document 141: Precision Estimates for AASHTO Test Method T 104 Determined Using AMRL Profi- ciency Sample Data, 2009. http://www.trb.org/Main/ Public/Blurbs/Precision_Estimates_for_AASHTO_ Test_Method_T_105_D_162186.aspx. 2. Azari, H. and R. Lutz, NCHRP Web-Only Document 140: Precision Estimates for AASHTO Test Methods T 186, T 154, and T 22, Determined Using CCRL Pro- ficiency Sample Data, 2009. http://www.trb.org/Main/ Public/Blurbs/Precision_Estimates_for_AASHTO_ Test_Methods_T_186_162157.aspx. 3. Azari, H. and R. Lutz, NCHRP Web-Only Document 139: Precision Estimates For AASHTO Test Method T 105 Determined Using CCRL Proficiency Sample Data, 2009. http://www.trb.org/Main/Public/Blurbs/ Precision_Estimates_for_AASHTO_Test_Method_ T_104_D_162224.aspx. 4. Azari, H., P. Spellerberg, and R. Lutz, NCHRP Web-Only Document 142: Precision Estimates for AASHTO T 242, 2009. http://www.trb.org/Main/ Public/Blurbs/Precision_Estimates_of_AASHTO_ T_242_162225.aspx. 5. Holsinger, R.E., A. Fisher, and P.A. Spellerberg, NCHRP Web-Only Document 71: Precision Esti- mates for AASHTO Test Method T308 and the Test Methods for Performance-Graded Asphalt Binder in AASHTO Specification M320, 2005. http://onlinepubs. trb.org/onlinepubs/nchrp/nchrp_w71.pdf. Table 11 Precision estimates of friction number Acceptable Range of Condition of Test Standard Deviation Two Test Results (d2s), and Test Property (1s)* Percent Single-Operator Precision 0.83 2.35 Multi-Laboratory Precision 1.90 5.37 *These limits are determined from data obtained during the calibration and testing of state friction systems at the field test centers at the Texas Transportation Institute and the Transportation Research Center.

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