Standard Reference Clinkers

Weigand (1994) reported the point-count results of the ASTM microscopy task group on one of the Standard Reference Clinkers supplied by the National Institute of Standards and Technology (Gaithersburg, Maryland). Compared to the Bogue calculations, the microscopical data are roughly 5% higher for alite, 5% lower for belite, 4% lower for C A, and 0.5% lower for ferrite. It was further shown that 3000 points per sample would provide sufficient data for statistical acceptance of port-land cement clinker polished sections. 

The National Institute of Standards and Technology (NIST) offers a set of Standard Reference Clinkers for phase abundance. Analysis of these clinkers by SEM, light microscopy, and QXRD isfound inStutzman... 

Stutzman, P. and Leigh, S., Phase Composition Analysis of NIST Reference Clinkers by Optical Micoscopy and X-ray Powder Diffraction, NIST Technical Note 1441, Appendix B, Selective Extractions for Clinker and Cement, NIST-National Institute of Standards and Technology, Washington, D.C., 2002. 

With any form of the internal standard method, it is necessary to employ reference standards that are as near as possible to the phases in the material as regards composition, polymorphism and degree of crystallinity. This implies both knowledge of the characteristics of the particular clinker under examination and the ability to prepare the necessary specimens, or alternatively to isolate them physically from the clinker itself. One solution (G30) has been to prepare reference patterns for a wide range of specimens of each phase and to use those that appear to correspond most closely to those present in the clinker under examination. Clinkers for which results had been obtained by point counting have also been used (K11). 

The experimental considerations applying to calcium silicate pastes (Sections 5.1 and 5.2) are equally relevant to cement pastes. Of the methods so far used in attempts to determine the degrees of reaction of the individual clinker phases as a function of time, QXDA (C39,D12,T34,P28) has proved much the most satisfactory. Procedures are essentially as for the analysis of a clinker or unreacted cement (Section 4.3.2), but it is necessary to take account of overlaps with peaks from the hydration products, and especially, with the C-S-H band at 0.27-0.31 nm. The water content of the sample must be known, so that the results can be referred to the weight of anhydrous material. If a sample of the unhydrated cement is available, and its quantitative phase composition has been determined, it may be used as the reference standard for the individual clinker phases in the paste. 

In Table 1.4 the content of components in European cements, according to standard EN 197-1 was given. As a rule it was establish that the share of clinker and mineral additions is eqital 100 %, and the gypsum content refers to the total and its addition, or anhydrite, is the resirlt of normalised SO3 content, which threshold values are 3.5 % or 4% (Table 1.3)... 

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