As SRM 114p is widely used in the cement industry for calibration of the Blaine measurement, it is an appropriate choice to be used as a reference material for PSD determination. Various PSDs were obtained by statistically analyzing the data obtained from round robin participants. From this study, two curves were developed, one for LAS-W and one for LAS-D. As shown in Fig. 9, the two curves do not differ significantly. Therefore, it could be argued that only one curve should be provided as reference. Nevertheless, the authors suggest that at this point the two curves should be provided. Further knowledge on this issue will be gained when the next generation of SRM 114 is developed by NIST.
The mean PSD curves obtained from the round robin tests have been added to the certificate for SRM 114p as informational data (i.e., not certified). The supplies of SRM 114p available at NIST cover industry needs until about summer 2004. Therefore, NIST initiated (2003) the procedure for securing and characterizing the next SRM 114 material. The certificate for the new SRM 114 will also include a reference PSD based on the LAS technique. A statistically meaningful reference PSD for techniques other than LAS was not possible, due to the low number of corresponding data sets obtained from the most recent round robin study.
FIG. 9−Graphical comparison between the distributions calculated for only the LAS-W (Table 1) or LAS-D data (Table 2). For clarity, the confidence intervals are not shown here, but can be found in the corresponding tables.