Synthesis Mechanism and Material Characterization of C4AF Obtained by the Self-propagating Combustion Reaction Method

Abstract

To investigate the influence of preparation process on the properties of synthesized C4AF, the powder was prepared via the self-propagating combustion reaction (SPCR) method using urea as fuel and metal nitrates as cation precursors. Synthesis mechanism of the SPCR method, calculation and adjusting principles of urea dosage were detailedly introduced. Material characterization of synthesized C4AF was performed with the aid of X-ray diffractometry, Fourier transform infrared spectrometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, 27Al nuclear magnetic resonance and isothermal microcalorimetric technique. Remaining content of transition phase of calcium carbonate in synthesized C4AF was determined by quantitative analysis of X-ray diffractometry. It was found that there was no difference in the hydration behavior of C4AF synthesized by the SPCR method and the traditional solid-state reaction (SSR) method. C3AH6 and amorphous iron (III) hydroxide (Fe(OH)3) would be formed during the hydration of C4AF while CH not. Crystallite size of synthesized C4AF was 16.1 A and the apparent activation energy was 36.2 kJ/mol. Coordinated condition of Al in C4AF can be detected by 27Al NMR technique, but the peaks were broadened and the intensities were relatively low, supporting the use of 27Al NMR for the quantitative analysis of C3A in Portland cements.