Phase Analysis of Hydraulic Cements by X-Ray Powder Diffraction: ASTM Precision, Bias, and Qualification
Paul E. Stutzman, Stefan D. Leigh
Cements classification is based, in part, upon phase composition. Traditionally, estimates of composition have been made using bulk chemical analyses and the Bogue calculations that were developed over 75 years ago. Since their introduction, these calculations have been recognized as only approximations to the true phase composition, as their inherent phase chemistry assumptions do not accurately reflect the chemistry of industrial clinkers. X-ray powder diffraction analysis provides an alternative approach to direct phase determination. Application of the Rietveld method for refinement of multi-phase powder diffraction patterns provides a means to improve the analysis of complex cement diffraction patterns through its whole-pattern approach and ability to determine the best-fit set of diffraction patterns that make up the composite pattern of cement.To estimate inter- and intra-laboratory precision and bias and to establish qualification criteria, a round-robin analysis involving 11 laboratories was undertaken. Four cement reference specimens were prepared using NIST SRM clinkers spiked with known amounts of one or more of gypsum, bassanite, anhydrite, and calcite. Participants were instructed to analyze the whole cement, collect data in triplicate, and repack the specimen for each run. All participating laboratories had some experience with both Rietveld analysis and hydraulic cements. Implicit in this exercise is the ability to identify phases in the cements and apply a logical
and Leigh, S.
Phase Analysis of Hydraulic Cements by X-Ray Powder Diffraction: ASTM Precision, Bias, and Qualification, ASTM Journal of Testing and Evaluation
(Accessed May 28, 2023)