Rietveld full-profile quantification of Portland cement clinker: The importance of including a full crystallography of the major phase polymorphs

Abstract

Crystalline phases present in the three NIST SRM Standard Portland cement clinkers 8486, 8487, and 8488 have been quantified from XRD powder patterns, (CoKα radiation), using the full-profile Rietveld method. Included in the Rietveld refinement are rhombohedral (R), monoclinic (M), and triclinic (T) crystal polymorphic forms of C3S, as well as crystal polymorphs of C2S and C3A. It is necessary to specify the phase crystallography including polymorphs, because of the extreme superposition of alite and belite XRD lines in the clinker patterns. Unsatisfactory results occur when only one or two of the C3S polymorphs are used in the Rietveld quantification; best results occur when all three polymorphs for C3S are included. The latter are called RMT-type refinements. The Rietveld full-profile XRD method is as precise as the microscope point-counting (MPC) method, but much less labor-intensive. The Rietveld method can quantify the C3S phase polymorphs, as well as total C3S. Rietveld and MPC methods give the same phase weight percentages for the three NIST standard clinkers. Calculated oxide weight percentages obtained from Rietveld phase weight percentages agree well with oxide percentages determined by XRF analysis. Bogue mineral weight percentages do not agree with Rietveld or MPC data, while transformation of the Bogue mineral percentages to oxides does not compare well with XRF analysis.

Rietveld Quantitative Phase Analysis of OPC Clinkers, Cements and Hydration Products

“…Soon after, other works showed the advantages of this method which does not require standards or calibration curves (Moller 1995(Moller , 1998Meyer et al 1998;Taylor et al 2000). Initially, the studies were focused on OPC clinkers and later expanded to different types of cements.…”

Tricalcium Silicate T1 and T2 Polymorphic Investigations: Rietveld Refinement at Various Temperatures Using Synchrotron Powder Diffraction

“…A link between tricalcium silicate polymorphism and the strength of the cement was demonstrated by Stanìk and Sulovský 18 (although no reference to the earlier works of Harada et al 15 or Mascolo et al 17 was made). Taylor et al 19 and Peterson et al 20 recently highlighted the importance of including tricalcium silicate polymorphs in the Rietveld model for the phase quantification of cement clinker and noted that quantitative analysis of these polymorphs can be obtained using powder diffraction and Rietveld analysis.…”

Direct mineralogical composition of a MgO-C refractory material obtained by Rietveld methodology

“…The method is standardless but the crystal structures of all the phases present in the sample must be known as the process comprises the comparison of the measured and calculated patterns. Rietveld QPA has been successfully applied to simple mixtures 30,31 and in the last years it has been employed to more complex industrial materials such as ordinary Portland clinkers and cements, [32][33][34] calcium aluminate cements, 35 mineralised Portland clinkers 36 and porcelains. 37 This methodology has several advantages over others because it uses a wide diffraction range minimizing peak overlap, preferred orientation and sample broadening effects.…”