Direct Determination of Phases in Portland Cements by Quantitative X-Ray Powder Diffraction
Paul E. Stutzman
The transformation of chemical analyses to phase estimates via the Bogue calculations has been successfully used by industry for the past 70 years. Since its inception, however, it has been recognized as an estimate of potential phase composition based upon implicit assumptions that are neither correct nor complete. Other methodologies for the direct determination of phases in cements have been sought for potentially more accurate and more complete accounting of the actual phase composition of cements. Direct measurements of phase composition should provide a better basis for relating mineralogical composition to performance characteristics, and improving predictive capability for cements. Quantitative determination of cement phase composition has been performed by X-ray powder diffraction for over 50 years. These analyses required both careful preparation of calibration curves and measurement of the peak intensities from the resulting diffraction patterns. Difficulties encountered in these analyses include the matching of standards to the industrial phases due to the influences of chemical and structural variation on the phase patterns and measurement of diffraction peak intensities. Recent development of the Rietveld method for X-ray powder diffraction for multi-phase mixtures provides a means to overcome the difficulties of the earlier XRD analyses, resulting in a renewed interest in powder diffraction and a quantitative mineralogical tool. Statistical analyses of companion Bogue (ASTM C150) and quantitative X-ray powder diffraction (QXRD) estimates for cement phases are used to establish the most likely linear relationship between these two measurement techniques for alite, belite, aluminate, ferrite, and for the combinations (C3S+4.75·C3A) and (C4AF+2·C3A) used to characterize heat of hydration and sulfate resistance, respectively. This cross- calibration was performed using published data from more than 194 cements, spanning more than 50 years of manufacture.
Direct Determination of Phases in Portland Cements by Quantitative X-Ray Powder Diffraction, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=907364
(Accessed October 4, 2023)