Nanosized belite phases obtained by flame spray pyrolysis: Assessment of process conditions on the mineralogy and reactivity

Abstract

The synthesis of highly reactive dicalcium silicate phases by the alternative method flame spray pyrolysis (FSP) was investigated. Five main conditions of the synthesis process were varied and analyzed by applying a two-level fractional factorial design 25–2 resolution III, with a replica of a chemical system defined by a mixture of Ca(O2CCH2CH3)2/Si(C2H5O))4 dissolved in ethanol/water/triethanolamine to evaluate the formation of polymorphs and their reactivity. For this, a physical and mineralogical characterization was carried out that included X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) specific surface area analysis, thermogravimetric analysis (TGA-DSC), and transmission electron microscopy (TEM). The investigation reveals that the process parameters have a remarkable importance on the final properties of the samples, favoring the formation of belite phases with high reproducibility. The hydraulic samples present a complete hydration reaction after 24 h of contact with water, giving a clear image of the potential of this technique for the development of highly reactive materials that can be part of sustainable construction in the future.