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A new Standard Reference Materialtextsuperscript® (SRM) for portland cement clinker has been produced for the Office of Standard Reference Materials at the National Institute of Standards and Technology (NIST). The SRM clinkers are intended for use in developing and testing quantitative methods of phase analysis for portland cement and cement clinker. The new SRM is one of three clinkers available from NIST representing the range of textures and compositions of North American clinker production. As the original SRM stock for SRM 2687 has been depleted, new material was obtained that retained the fine-grained texture of that SRM. Certification of the phase composition of the clinker is based upon consensus means and uncertainties of two independent analytical methods: scanning electron microscopy with image analysis and x-ray powder diffraction (XRD) analyses. The XRD data were subdivided to provide two separate sample sets processed separately using two different Rietveld refinement codes. These codes differed slightly in the determination of the silicate phases, which have very similar powder diffraction patterns and can be difficult to decompose. Therefore, the input data set for determining the consensus means, uncertainties and informational values is composed of two distinct XRD phase abundance estimates and one SEM/image analysis set of estimates. The XRD data are close to that determined by microscopy, but some distinct differences are seen. The disagreements may reflect the difficulty in resolving the fine-sized aluminate and ferrite interstitial phases using the microscope and challenges in decomposing highly overlapped powder diffraction data. The XRD data do display greater precision than replicate measurements by microscopy, likely the result of the specimen homogenization resulting from grinding the clinker to a powder. The certified reference values are consensus values, calculated by combining the results from both measurement techniques using the DerSimonian-Laird method with the standard uncertainties based upon the Horn-Horn-Duncan variance estimate. Reference values are best estimates based upon a single measurement technique. Reference values are provided for phases periclase, arcanite, aphthitalite, and lime and for the bulk oxides from x-ray fluorescence analysis.

Certification of standard reference material SRM2687a, Portland cement clinker