Certification of the phase compositions of the NIST Reference Clinkers often is based upon more than one independent method. The current certificate values were established using an optical microscope examination, and additional microscope data taken from an ASTM C 1356 round robin. The X-ray powder diffraction (XRD) study provides the second, independent estimate of the phase abundances, with the experiment designed to evaluate inter- and intra-vial homogeneity. Reitveld analysis of the powder diffraction patterns allowed calculation of a set of best-fit reference patterns and their scale factors. Because of significant contrast in the linear absorption coefficients of ferrite and periclase relative to the estimated mean matrix linear absoption coefficient, the scale factors were adjusted for microabsorption effects using the and the adjusted scale factors used to calculate phase abundance. The XRD data agree with the optical data with the exception of aluminate. This disagreement may reflect the difficulty in resolving this finely-crystalline phase using the optical microscope. The XRD data did show greater precision than replicate measurements by microscopy.Measurements from different sources, laboratories, instruments, and from different methods can exhibit significant between-method variability, as well as distinct within-method variances. The two data sets are treated using three methods to establish the best-consensus values and to provide meaningful uncertainties. While the mean values of the individual phase abundances do not vary, the 95 % uncertainty level values do. One method of combining the data sets was favored as this method produces a weighted mean whose weighting scheme does not necessarily skew the consensus value in the direction of the large number of XRD values.
Proceedings Title: Cement Microscopy, International Conference | 22nd | | International Cement Microscopy Association
Conference Dates: April 29-May 4, 2000
Conference Location: Quebec, -1
Conference Title: Proceedings of the International Conference on Cement Microscopy
Pub Type: Conferences
cement, clinker, composition, microscopy, phase, x-ray powder diffraction