Precision Statements for AASHTO Standard Methods of Test T 148, T 265, T 267, AND T 283 (2011) / Chapter Skim
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FINDINGS AASHTO T 148, "Measuring Length of Drilled Concrete Cores" An ILS was conducted to prepare precision estimates for AASHTO T 148, "Measuring Length of Drilled Concrete Cores." Six drilled concrete cores with varying dimensions and surface roughness were obtained from several test sections in the FHWA's Long-Term Pavement Performance program. The cores were delivered to 11 laboratories, where the length of each core was measured using a 3-point caliper described in AASHTO T 148.
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The resulting standard deviations and the allowable range of differences between two results within one laboratory and between different laboratories are presented in Table 3. AASHTO T 265, "Laboratory Determination of Moisture Content of Soils" An ILS was conducted to prepare precision estimates for AASHTO T 265, "Laboratory Determination of Moisture Content of Soils." Test data were collected for four aggregate-soil blends judged suitable for base and subbase construction.
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4-in.-diameter 0.9 2.4 6-in.-diameter 1.8 4.9 Table 3 Precision estimates for measurement of drilled concrete cores based on AASHTO T 148 Repeatability (S r ) Reproducibility (S R )
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Therefore the computed precision estimates from the two blends are presented separately in the proposed precision statement. Table 8 presents the precision estimates for moisture content determination based on the results of the 4 Repeatability (S r )
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AASHTO T 267, "Determination of Organic Content in Soils by Loss on Ignition" An interlaboratory study was conducted to prepare precision estimates for AASHTO T 267, Determination of Organic Content in Soils by Loss on Ignition." Samples from three types of soils (clay, silt, and sand) were each blended with three different percentages (2%, 5%, and 8%)
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6Repeatability ReproducibilitySoil Type Design Organic Content No. of Labs Average Measured Organic Content Sx 1s (Sr)
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to MoistureInduced Damage" An interlaboratory study was conducted to prepare precision estimates for AASHTO T 283, "Resistance of Compacted Hot Mix Asphalt (HMA) to Moisture-Induced Damage." Two different sources of aggregates -- limestone and sandstone -- with varying levels of moisture resistivity and two methods of compaction -- gyratory and Marshall -- were selected for the study.
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Once identified for elimination, the same data were eliminated from any smaller subsets analyzed. The precision estimates of AASHTO T 283 are presented in Table 16.
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