Associate professor, University of British Columbia, Vancouver, B.C.
Measures of the within- and between-laboratory variability associated with the standard test method for determining the compressive strength of cylindrical portland cement concrete specimens have been derived from data obtained in three interlaboratory testing programs operating in western Canada. These data have been analyzed using appropriate ASTM standard practices to provide estimates of repeatability (within-laboratory) and reproducibility (between-laboratory) standard deviation values and corresponding precision indices (difference “two”-standard-deviation limits). Both measures of variability have been found to vary linearly with the compressive strength of the test concrete, and hence the standard deviation and precision values are best expressed as linear functions of this strength. The resulting reproducibility (between-laboratory) precision index values are particularly important in that they provide guidance as to the level of the component of variability to be expected when two or more laboratories are testing the same batch of portland cement concrete for its compressive strength.
Paper ID: CCA10384J