Abstract:

Clinker calcination is a critical stage that influences the energy consumption in Portland cement production, and improving the efficiency of clinker manufacturing is a major concern in cement chemistry. This paper focuses on the synthesis of tetra-calcium aluminoferrite (C₄AF) at low temperatures with soluble metallic nitrate and urea as raw materials using the self-propagating combustion reaction (SPCR) method. We systematically analyze the mineral phase composition, crystallinity, particle morphology, and hydration behavior of the synthesized C₄AF using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and isothermal microcalorimetry. Our findings demonstrate that high-purity C₄AF can be successfully synthesized via the SPCR method at 500 ℃ for 2 hours. The optimal raw material ratio by weight is m_{\mathrm{C}\mathrm{a}(\mathrm{N}{\mathrm{O}}_3{)}_2·4{\mathrm{H}}_2\mathrm{O}}∶ m_{\mathrm{A}\mathrm{l}(\mathrm{N}{\mathrm{O}}_3{)}_3·9{\mathrm{H}}_2\mathrm{O}}∶ m_{\mathrm{F}\mathrm{e}(\mathrm{N}{\mathrm{O}}_3{)}_3·9{\mathrm{H}}_2\mathrm{O}}∶ m_{\mathrm{C}\mathrm{O}(\mathrm{N}{\mathrm{H}}_2{)}_2}=1.259∶1.0∶1.077∶2.664. CaCO₃ is the only transient phase during the formation of C₄AF. Increasing the urea dosage effectively raises reaction temperature and enhances the crystallinity of the synthesized C₄AF. Additionally, the synthesized C₄AF exhibits high hydration activity with only one peak observed in the hydration heat release curve during the initial 30 minutes. No dormancy period is observed, and the calculated hydration heat at complete hydration is 474 J/g.

Key words: portland cement, clinker, tetra-calcium aluminoferrite, self-propagating combustion reaction, low temperature