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Certification of Standard Reference Material® 2686b Portland Cement Clinker



N. Alan Heckert, Laura Mundy, Paul E. Stutzman


A new Standard Reference Material® (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 representing the range of textures and compositions of North American clinker production. SRM 2686b is a medium-grained, heterogeneous phase distribution clinker similar in phase composition and texture to the original SRM 2686. Certification of phase abundance was accomplished using quantitative x-ray powder diffraction and scanning electron microscopy with image analyses. These methods provide mutually unique means to establish phase abundance, which subsequently are combined to establish certified values and uncertainties. This clinker differs from the earlier SRMs by the presence of -C2S. Since SEM imaging does not distinguish between the  and  polymorphs of C2S, a certified value representing the combined mass fraction is provided and informational values are provided for the individual polymorph fractions. For alkali sulfates and free lime, phase abundance is established using a single method (XRD) so only informational values are provided. While the XRD data are close to that of microscopy, 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
Special Publication (NIST SP) - 260-204
Report Number


Cement clinker, consensus means, image analysis, microscopy, quantitative analysis, Rietveld analysis, x-ray powder diffraction.


Heckert, N. , Mundy, L. and Stutzman, P. (2021), Certification of Standard Reference Material® 2686b Portland Cement Clinker, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed April 17, 2024)
Created April 12, 2021, Updated October 12, 2021