Precision Estimates of AASHTO T148: Measuring Length of Drilled Concrete Cores (2010)

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20 APPENDIX C- PRECISION STATEMENT FOR AASHTO T148

21 PRECISION STATEMENT FOR AASHTO T148, “STANDARD METHOD OF TEST FOR MEASURING LENGTH OF DRILLED CONCRETE CORES” 1 Precision and Bias 1.1 Precision - Criteria for judging the acceptability of length of drilled concrete cores obtained by this method are given as follows: 1.1.1 Single-Operator Precision (Repeatability) – The figures in Column 2 of Table 1 are the standard deviations that have been found to be appropriate for the length of drilled concrete cores. Two results obtained in the same laboratory, by the same operator using the same equipment, in the shortest practical period of time, should not be considered suspect unless the difference in the two results exceeds the single-operator limits given in Table 1, Column 3. 1.1.2 Multi-laboratory Precision (Reproducibility) – The figures in Column 2 of Table 1 are the standard deviations that have been found to be appropriate for the length of drilled concrete cores. 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 multi-laboratory limits given in Table 1, Column 3. Table 1 – Precision Estimates for AASHTO T148 Property and Type Index Standard Deviation a (mm) Acceptable Range of Two Results a (mm) Single-Operator precision: 4" Diameter 6" Diameter 0.4 0.7 1.0 1.9 Multi-laboratory Precision: 4" Diameter 6" Diameter 0.9 1.8 2.4 4.9 a These values represent the 1s and d2s limits described in ASTM Practice C670. Note – The precision estimates are based on the analysis of test results from 11 laboratories participated in an AMRL round robin study. The data consisted of length measurements of six drilled concrete cylinders having diameter of 4 in. and 6 in. and height of 4” to 10”. The details of this analysis are in NCHRP Web- Only Document 165. 1.2 Bias– No information can be presented on the bias of the procedure because no comparison with the material having an accepted reference value was conducted.