Determination of amorphous phase levels in Portland cement clinker

Abstract

The existence of glass or amorphous component in Portland cement clinker has been questioned for a long time. However, besides the crystalline phases, there are reports in the literature of noncrystalline material in cement clinker, which is considered to be the residue of the melt that has failed to crystallize. Absolute phase abundances were determined in this study by Rietveld refinements with laboratory X-ray data, using both internal and external phase composition standards. The results clearly demonstrate the existence of an amorphous component in Portland cement clinker. The presence of an amorphous component was also apparent from diffraction data for clinker from which the silicate phases had been chemically removed, using both laboratory X-ray and synchrotron radiation patterns.

Hydration studies of calcium sulfoaluminate cements blended with fly ash

“…Table 1 shows RQPA (Rietveld Quantitative Phase Analysis) for cement (CS10-25) and fly ash anhydrous powders, including ACn. The ACn content of this CSA cement,~15 wt.%, is slightly higher than that found for OPC cements,~10 wt.% [41,42], likely due to the lower clinkering temperature leading to smaller particle sizes and microstrains and defects-bearing crystals. The crystal structure descriptions for each phase were those detailed elsewhere [15], except for ye'elimite, where a reviewed orthorhombic C 4 A 3 S has been used [43].…”

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“…The materials examined in their study, National Institute for Science and Technology (NIST) Standard Reference Materials (SRM) 8486-8488 clinkers and two Australian clinkers, are different from those in this work, but the values stated in their paper (from 6.1 to 15.9%) suggest that our results are reasonable. Unfortunately, these authors do not have access to the NIST SRM 8486-8488 clinkers and are unable to directly repeat or confirm the results of Suherman et al [4].…”

“…Their most crystalline samples were slow cooled to promote crystallization. These results seem to have been largely forgotten, but a few papers have recently appeared [4,5] which use X-ray based techniques to determine the amorphous content in clinker, and various single phase cement-related materials. One conclusion that may be drawn from these results, is the amorphous contents of these materials are very sensitive to synthesis conditions and can vary significantly.…”

“…Another author studied a range of single-phase materials using a standardless X-ray technique (the Ruland method), and found wildly varying amorphous contents for the same compound [5]. Very recently a paper appeared citing values for amorphous contents from Rietveld analysis of between 6 and 15% for a number of cement clinkers [4]. The materials examined in their study, National Institute for Science and Technology (NIST) Standard Reference Materials (SRM) 8486-8488 clinkers and two Australian clinkers, are different from those in this work, but the values stated in their paper (from 6.1 to 15.9%) suggest that our results are reasonable.…”

Rietveld quantitative phase analysis of Yeelimite-containing cements

“…To overcome this problem, two approaches have been developed, the internal and the external standard methods (to be briefly described just below). The presence of a glassy or amorphous component in Portland cements and clinkers has been debated by several authors [29][30][31]. I) Internal standard method or "spiking method", which consists on the addition of a known amount of a crystalline standard, W st .…”