Effect of Ti on crystal transition and solid solution characteristics of white Portland cement clinker

Titanium (Ti) is a common trace element in white Portland cement clinker. Ti⁴⁺ generally replaces Si⁴⁺ to form a solid solution in silicate minerals, which has an important influence on the mineral crystal form of white cement clinker. In this paper, the effects of Ti on the mineral composition and solid solution characteristics of white Portland cement clinker were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM-EDS) and Rietveld quantitative analysis. The results showed that the incorporation of titanium dioxide (TiO₂) stabilised the highly active α′_H-belite (C₂S), but over 1% will form calcium titanate (CaTiO₃) The crystal form of alite (C₃S) was T3→M1→M3→R with the increase of titanium dioxide content. Ti elements tended first to be solid soluble in the intermediate phase, then C₂S, and finally C₃S. The content of Ti in α′_H-C₂S was higher than that in β-C₂S. With the increase of titanium dioxide content, the calcium–silicon ratio of C₂S decreased first and then increased. In silicate minerals, Ti⁴⁺ replaced Si⁴⁺ to form titanate [TiO₄]. The Ca²⁺ ion in α′_H-C₂S was placed in a more electronegative environment, resulting in a larger binding energy of electrons in the 2p orbit.