The authors thank ASTM Task Group C01.25.01 and the chairman Charles Buchanan Jr. for providing the opportunity for these round robins and subsequent analysis. We thank all participants of the round robin studies (listed in references [Ferraris et al., 2002a, 2002b]) for providing time and staff to perform the tests. We thank Robin Haupt and the staff of the Cement and Concrete Reference Laboratory (CCRL), who provided the cement samples, and Lin Lum of the Ceramics Division who performed the laser diffraction measurements at NIST.