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The optimization of parameters of synthesis of belite cement clinker from coal fly ash of high Ca content is presented in this paper. The synthesis process is based on the hydrothermal-calcination-route of the fly ash without extra additions. The hydrothermal treatment was carried out in demineralized water and a 1 M NaOH solution for 4 h at the temperatures of 100 degrees C, 150 degrees C, and 200 degrees C. The precursors obtained during the hydrothermal treatmentwere heated at temperatures of 700 degrees C, 800 degrees C, 900 degrees C, and 1000 degrees C. The changes of fly ash composition after the different treatments were characterized by X-ray diffraction (XRD), FT infrared (FTIR) spectroscopy, surface area (BET-N2), and thermal analyses. From the results obtained we concluded that the optimum temperature of the hydrothermal treatment was 200 degrees C, and the optimum temperature for obtaining the belite cement clinker was 800 degrees C.

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The study of the hydration reactions of Portland cement is well documented by conventional techniques such as X‐ray diffraction, differential thermal and thermogravimetric analysis, or NMR, for instance. However, a complete view of all the phases present in the reactions is elusive. In this study, by using an in situ analysis through confocal Raman microscopy (CRM), the reaction of the initial phases (C2S, C3S, and C3A) to form new crystalline phases (portlandite, ettringite, and monosulfate) and amorphous C‐S‐H gel is reported. For the first time, this characterization technique allows to know the distribution and evolution of hydration water. In situ characterization of cement‐based materials opens a new gate to understand the different mechanisms involved in the processes of hydration of a Portland cement, due to the combined chemical and high spatial resolution of CRM.

The microstructure and mechanical performance of two low energy fly ash belite cements (FABC-1-W and FABC-1-N) obtained from high calcium-coal fly ash as raw material is studied in this work. The FABC were obtained after a previous hydrothermal treatment of the fly ash in demineralized water and NaOH 1M solution. The hydration of both FABC-1-W and FABC-1-N during 180 days was followed by thermal analysis, X-ray diffraction, FT infrared spectroscopy, scanning electron microscopy and Brunauer-Emmett and Teller-N 2 surface area measurements. The mechanical properties were studied under different curing conditions: normal (211C and o95% RH) and accelerated (401C and o95% RH). Porosity and pore-size distribution were also studied. The results showed a better mechanical performance for FABC-1-N when the curing was normal and a better mechanical performance for FABC-1-W when the curing was accelerated. 1845J ournal

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