From this round-robin test, the most frequently used PSD measurement technique by the industry is LASER diffraction with dispersion of cement in a liquid. The SEM method, as applied in the current test, is relatively new and was used by only one participant in the round robin. Similarly, the sedimentation method was used by only one participant and it did not report data below 3 µm; it should be determined if this represents the complete PSD or if it is a reporting issue. There were two sets using EZS, but both were determined to be outliers based on measurements of the reference material SRM 114p. Because the scope of the ASTM committee is to determine the best method or methods to measure PSD of cement, the methods to be standardized should be carefully selected. In other words, the committee should concentrate its initial efforts on the most widely used and most promising measurement methods (e.g., wider range of size and better reproducibility).
In this first round-robin test, there was not enough information collected to be able to definitively determine the reference distribution using SRM 114p or to determine the best methods to measure the cement PSD. Therefore, the following recommendations should be considered in organizing the next round-robin:
It is the belief of the authors that an ASTM standard should include a standard procedure for each method that is specialized for cement. It would certainly help if a reference distribution for a cement such as SRM 114p could be determined. This will help the operator determine if the PSD measured is within an acceptable error margin.
In conclusion, before a standard test can be proposed, further research needs to be conducted to determine the correct methodology for any of the tests discussed in this report.