Microstructure and mechanical performance of belite cements from high calcium coal fly ash

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-l-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-N₂ surface area measurements. The mechanical properties were studied under different curing conditions: normal (21°C and <95% RH) and accelerated (40°C and <95% RH). Porosity and pore-size distribution were also studied. The results showed a better mechanical performance for FABC-l-N when the curing was normal and a better mechanical performance for FABC-1-W when the curing was accelerated.