X-ray mapping of interstitial phases in sulphate resisting cement clinker

Abstract

Industrial sulphate-resisting cement clinker has been investigated by elemental mapping and X-ray microanalysis (EDS) in a scanning electron microscope; powder X-ray diffraction (XRD) and X-ray fluorescence analysis. The interstitial material mainly consists of ferrite Ca2·01(07)Al0·71( 7)Fe0·89(6)Mg0·08(2)Mn0·05(2)Si0·16(4)Ti0·03(1)P0·009(3) O5 (EDS), plus minor amounts of an orthorhombic aluminate (XRD) and potassium sulphate (EDS). In the elemental maps (Ca, Si, Al, Fe, K. S), recorded using the characteristic Ka X-rays; alite, belite, ferrite, potassium sulphate and pores are readily identified, while aluminates are only rarely distinguishable. Free lime, periclase, unreacted silica, and secondary alite should be easy to recognize, but were not observed. Chlorine or sodium were not detected in the clinker. More potassium sulphate was associated with belite, than with a lite, and the texture of the interstitial potassium sulphate suggests that at high temperature, molten potassium sulphate wets the belite crystals, but not the alite crystals.